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	$196.43	7.284%	$210.738	$210.74	$210.75	$210.70
Purchase #2	$20.80	8.363%	$22.5395	$22.54	$22.55	$22.50
Purchase #3	$229.87	10.578%	$254.1856	$254.19	$254.20	$254.20
Purchase #4	$137.50	13.314%	$155.8068	$155.81	$155.80	$155.80
Purchase #5	$70.47	3.398%	$72.8646	$72.86	$72.85	$72.90
Purchase #6	$81.67	9.538%	$89.4597	$89.46	$89.45	$89.50
Purchase #7	$130.53	13.554%	$148.222	$148.22	$148.20	$148.20
7 purchase totals =	$867.27		$953.8162	$953.82	$953.80	$953.80