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	$69.35	9.713%	$76.086	$76.09	$76.10	$76.10
Purchase #2	$31.51	6.743%	$33.6347	$33.63	$33.65	$33.60
Purchase #3	$84.53	6.621%	$90.1267	$90.13	$90.15	$90.10
Purchase #4	$228.37	12.552%	$257.035	$257.04	$257.05	$257.00
Purchase #5	$55.69	5.109%	$58.5352	$58.54	$58.55	$58.50
Purchase #6	$58.44	4.454%	$61.0429	$61.04	$61.05	$61.00
Purchase #7	$165.46	4.126%	$172.2869	$172.29	$172.30	$172.30
7 purchase totals =	$693.35		$748.7474	$748.76	$748.85	$748.60