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	$100.73	3.507%	$104.2626	$104.26	$104.25	$104.30
Purchase #2	$236.73	9.788%	$259.9011	$259.90	$259.90	$259.90
Purchase #3	$208.52	6.642%	$222.3699	$222.37	$222.35	$222.40
Purchase #4	$56.39	6.229%	$59.9025	$59.90	$59.90	$59.90
Purchase #5	$202.88	10.238%	$223.6509	$223.65	$223.65	$223.70
Purchase #6	$203.40	8.762%	$221.2219	$221.22	$221.20	$221.20
Purchase #7	$152.26	11.713%	$170.0942	$170.09	$170.10	$170.10
7 purchase totals =	$1,160.91		$1,261.4031	$1,261.39	$1,261.35	$1,261.50