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	$84.55	5.189%	$88.9373	$88.94	$88.95	$88.90
Purchase #2	$233.51	11.142%	$259.5277	$259.53	$259.55	$259.50
Purchase #3	$168.67	4.441%	$176.1606	$176.16	$176.15	$176.20
Purchase #4	$11.90	6.410%	$12.6628	$12.66	$12.65	$12.70
Purchase #5	$91.78	8.613%	$99.685	$99.69	$99.70	$99.70
Purchase #6	$158.64	13.188%	$179.5614	$179.56	$179.55	$179.60
Purchase #7	$75.67	7.519%	$81.3596	$81.36	$81.35	$81.40
7 purchase totals =	$824.72		$897.8944	$897.90	$897.90	$898.00