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	$178.25	5.649%	$188.3193	$188.32	$188.30	$188.30
Purchase #2	$90.74	11.802%	$101.4491	$101.45	$101.45	$101.40
Purchase #3	$151.98	13.629%	$172.6934	$172.69	$172.70	$172.70
Purchase #4	$143.50	3.244%	$148.1551	$148.16	$148.15	$148.20
Purchase #5	$196.65	5.111%	$206.7008	$206.70	$206.70	$206.70
Purchase #6	$90.59	5.477%	$95.5516	$95.55	$95.55	$95.60
Purchase #7	$71.74	6.489%	$76.3952	$76.40	$76.40	$76.40
7 purchase totals =	$923.45		$989.2645	$989.27	$989.25	$989.30