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	$86.33	6.517%	$91.9561	$91.96	$91.95	$92.00
Purchase #2	$127.58	11.648%	$142.4405	$142.44	$142.45	$142.40
Purchase #3	$34.51	5.327%	$36.3483	$36.35	$36.35	$36.30
Purchase #4	$231.82	9.813%	$254.5685	$254.57	$254.55	$254.60
Purchase #5	$30.85	4.746%	$32.3141	$32.31	$32.30	$32.30
Purchase #6	$209.81	6.557%	$223.5672	$223.57	$223.55	$223.60
Purchase #7	$116.37	12.123%	$130.4775	$130.48	$130.50	$130.50
7 purchase totals =	$837.27		$911.6722	$911.68	$911.65	$911.70