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	$55.60	13.215%	$62.9475	$62.95	$62.95	$62.90
Purchase #2	$109.28	13.123%	$123.6208	$123.62	$123.60	$123.60
Purchase #3	$79.86	12.597%	$89.92	$89.92	$89.90	$89.90
Purchase #4	$130.39	13.741%	$148.3069	$148.31	$148.30	$148.30
Purchase #5	$189.86	4.459%	$198.3259	$198.33	$198.35	$198.30
Purchase #6	$53.48	12.604%	$60.2206	$60.22	$60.20	$60.20
Purchase #7	$217.70	12.260%	$244.39	$244.39	$244.40	$244.40
7 purchase totals =	$836.17		$927.7317	$927.74	$927.70	$927.60