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	$160.53	6.267%	$170.5904	$170.59	$170.60	$170.60
Purchase #2	$154.97	4.698%	$162.2505	$162.25	$162.25	$162.30
Purchase #3	$104.76	3.324%	$108.2422	$108.24	$108.25	$108.20
Purchase #4	$191.31	6.375%	$203.506	$203.51	$203.50	$203.50
Purchase #5	$103.48	6.783%	$110.499	$110.50	$110.50	$110.50
Purchase #6	$115.92	13.760%	$131.8706	$131.87	$131.85	$131.90
Purchase #7	$159.97	9.238%	$174.748	$174.75	$174.75	$174.70
7 purchase totals =	$990.94		$1,061.7067	$1,061.71	$1,061.70	$1,061.70