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	$229.81	11.147%	$255.4269	$255.43	$255.45	$255.40
Purchase #2	$19.34	6.747%	$20.6449	$20.64	$20.65	$20.60
Purchase #3	$19.86	12.683%	$22.3788	$22.38	$22.40	$22.40
Purchase #4	$96.70	3.128%	$99.7248	$99.72	$99.70	$99.70
Purchase #5	$192.38	13.825%	$218.9765	$218.98	$219.00	$219.00
Purchase #6	$59.31	9.347%	$64.8537	$64.85	$64.85	$64.90
Purchase #7	$63.33	13.286%	$71.744	$71.74	$71.75	$71.70
7 purchase totals =	$680.73		$753.7496	$753.74	$753.80	$753.70