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	$85.71	12.851%	$96.7246	$96.72	$96.70	$96.70
Purchase #2	$32.70	4.700%	$34.2369	$34.24	$34.25	$34.20
Purchase #3	$95.34	4.290%	$99.4301	$99.43	$99.45	$99.40
Purchase #4	$108.95	6.431%	$115.9566	$115.96	$115.95	$116.00
Purchase #5	$13.85	6.479%	$14.7473	$14.75	$14.75	$14.70
Purchase #6	$6.31	9.123%	$6.8857	$6.89	$6.90	$6.90
Purchase #7	$69.92	12.822%	$78.8851	$78.89	$78.90	$78.90
7 purchase totals =	$412.78		$446.8663	$446.88	$446.90	$446.80