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	$186.39	11.213%	$207.2899	$207.29	$207.30	$207.30
Purchase #2	$216.50	12.223%	$242.9628	$242.96	$242.95	$243.00
Purchase #3	$162.46	7.144%	$174.0661	$174.07	$174.05	$174.10
Purchase #4	$53.27	3.533%	$55.152	$55.15	$55.15	$55.20
Purchase #5	$131.49	11.412%	$146.4956	$146.50	$146.50	$146.50
Purchase #6	$24.59	11.825%	$27.4978	$27.50	$27.50	$27.50
Purchase #7	$127.33	10.696%	$140.9492	$140.95	$140.95	$140.90
7 purchase totals =	$902.03		$994.4134	$994.42	$994.40	$994.50