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	$129.86	9.554%	$142.2668	$142.27	$142.25	$142.30
Purchase #2	$230.54	5.752%	$243.8007	$243.80	$243.80	$243.80
Purchase #3	$60.52	11.797%	$67.6595	$67.66	$67.65	$67.70
Purchase #4	$235.53	8.809%	$256.2778	$256.28	$256.30	$256.30
Purchase #5	$119.38	3.681%	$123.7744	$123.77	$123.75	$123.80
Purchase #6	$69.64	10.629%	$77.042	$77.04	$77.05	$77.00
Purchase #7	$40.62	7.112%	$43.5089	$43.51	$43.50	$43.50
7 purchase totals =	$886.09		$954.3301	$954.33	$954.30	$954.40