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	$32.52	13.560%	$36.9297	$36.93	$36.95	$36.90
Purchase #2	$154.68	12.200%	$173.551	$173.55	$173.55	$173.60
Purchase #3	$174.59	4.614%	$182.6456	$182.65	$182.65	$182.60
Purchase #4	$127.48	7.649%	$137.2309	$137.23	$137.25	$137.20
Purchase #5	$47.83	12.557%	$53.836	$53.84	$53.85	$53.80
Purchase #6	$40.35	3.299%	$41.6811	$41.68	$41.70	$41.70
Purchase #7	$115.39	10.400%	$127.3906	$127.39	$127.40	$127.40
7 purchase totals =	$692.84		$753.2649	$753.27	$753.35	$753.20