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	$71.37	7.540%	$76.7513	$76.75	$76.75	$76.80
Purchase #2	$247.38	11.525%	$275.8905	$275.89	$275.90	$275.90
Purchase #3	$78.85	4.573%	$82.4558	$82.46	$82.45	$82.50
Purchase #4	$51.61	8.606%	$56.0516	$56.05	$56.05	$56.10
Purchase #5	$83.54	7.209%	$89.5624	$89.56	$89.55	$89.60
Purchase #6	$166.62	8.485%	$180.7577	$180.76	$180.75	$180.80
Purchase #7	$183.54	12.360%	$206.2255	$206.23	$206.25	$206.20
7 purchase totals =	$882.91		$967.6948	$967.70	$967.70	$967.90