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	$174.87	10.227%	$192.754	$192.75	$192.75	$192.80
Purchase #2	$223.73	7.623%	$240.7849	$240.78	$240.80	$240.80
Purchase #3	$58.54	5.168%	$61.5653	$61.57	$61.55	$61.60
Purchase #4	$118.67	11.139%	$131.8887	$131.89	$131.90	$131.90
Purchase #5	$101.81	4.164%	$106.0494	$106.05	$106.05	$106.00
Purchase #6	$115.90	5.300%	$122.0427	$122.04	$122.05	$122.00
Purchase #7	$62.50	13.835%	$71.1469	$71.15	$71.15	$71.10
7 purchase totals =	$856.02		$926.2319	$926.23	$926.25	$926.20