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	$98.49	7.129%	$105.5114	$105.51	$105.50	$105.50
Purchase #2	$98.52	13.432%	$111.7532	$111.75	$111.75	$111.80
Purchase #3	$116.92	5.316%	$123.1355	$123.14	$123.15	$123.10
Purchase #4	$26.59	4.199%	$27.7065	$27.71	$27.70	$27.70
Purchase #5	$221.99	10.574%	$245.4632	$245.46	$245.45	$245.50
Purchase #6	$14.96	5.317%	$15.7554	$15.76	$15.75	$15.80
Purchase #7	$158.88	10.218%	$175.1144	$175.11	$175.10	$175.10
7 purchase totals =	$736.35		$804.4396	$804.44	$804.40	$804.50