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	$112.55	13.156%	$127.3571	$127.36	$127.35	$127.40
Purchase #2	$153.79	12.140%	$172.4601	$172.46	$172.45	$172.50
Purchase #3	$157.30	4.758%	$164.7843	$164.78	$164.80	$164.80
Purchase #4	$42.41	3.799%	$44.0212	$44.02	$44.00	$44.00
Purchase #5	$159.50	7.633%	$171.6746	$171.67	$171.65	$171.70
Purchase #6	$178.27	9.221%	$194.7083	$194.71	$194.70	$194.70
Purchase #7	$220.27	6.135%	$233.7836	$233.78	$233.80	$233.80
7 purchase totals =	$1,024.09		$1,108.7892	$1,108.78	$1,108.75	$1,108.90