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	$38.54	5.479%	$40.6516	$40.65	$40.65	$40.70
Purchase #2	$19.52	13.868%	$22.227	$22.23	$22.25	$22.20
Purchase #3	$202.48	13.227%	$229.262	$229.26	$229.25	$229.30
Purchase #4	$54.37	3.873%	$56.4758	$56.48	$56.50	$56.50
Purchase #5	$175.86	11.847%	$196.6941	$196.69	$196.70	$196.70
Purchase #6	$18.79	10.527%	$20.768	$20.77	$20.75	$20.80
Purchase #7	$53.46	7.311%	$57.3685	$57.37	$57.35	$57.40
7 purchase totals =	$563.02		$623.4470	$623.45	$623.45	$623.60