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	$64.86	12.486%	$72.9584	$72.96	$72.95	$73.00
Purchase #2	$227.63	12.171%	$255.3348	$255.33	$255.35	$255.30
Purchase #3	$75.49	10.154%	$83.1553	$83.16	$83.15	$83.20
Purchase #4	$22.50	10.276%	$24.8121	$24.81	$24.80	$24.80
Purchase #5	$59.34	6.560%	$63.2327	$63.23	$63.25	$63.20
Purchase #6	$61.59	6.818%	$65.7892	$65.79	$65.80	$65.80
Purchase #7	$150.61	7.785%	$162.335	$162.34	$162.35	$162.30
7 purchase totals =	$662.02		$727.6175	$727.62	$727.65	$727.60