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	$85.90	12.827%	$96.9184	$96.92	$96.90	$96.90
Purchase #2	$75.69	10.789%	$83.8562	$83.86	$83.85	$83.90
Purchase #3	$124.82	13.795%	$142.0389	$142.04	$142.05	$142.00
Purchase #4	$228.89	9.223%	$250.0005	$250.00	$250.00	$250.00
Purchase #5	$174.43	9.601%	$191.177	$191.18	$191.20	$191.20
Purchase #6	$236.83	8.477%	$256.9061	$256.91	$256.90	$256.90
Purchase #7	$88.66	9.111%	$96.7378	$96.74	$96.75	$96.70
7 purchase totals =	$1,015.22		$1,117.6349	$1,117.65	$1,117.65	$1,117.60