Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.57	11.435%	$212.3617	$212.36	$212.35	$212.40
Purchase #2	$185.87	12.404%	$208.9253	$208.93	$208.95	$208.90
Purchase #3	$164.37	13.496%	$186.5534	$186.55	$186.55	$186.60
Purchase #4	$144.88	7.684%	$156.0126	$156.01	$156.00	$156.00
Purchase #5	$241.69	10.663%	$267.4614	$267.46	$267.45	$267.50
Purchase #6	$171.47	13.384%	$194.4195	$194.42	$194.40	$194.40
Purchase #7	$243.39	13.254%	$275.6489	$275.65	$275.65	$275.60
7 purchase totals =	$1,342.24		$1,501.3828	$1,501.38	$1,501.35	$1,501.40