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	$162.28	4.322%	$169.2937	$169.29	$169.30	$169.30
Purchase #2	$41.94	12.322%	$47.1078	$47.11	$47.10	$47.10
Purchase #3	$62.33	7.843%	$67.2185	$67.22	$67.20	$67.20
Purchase #4	$73.89	5.273%	$77.7862	$77.79	$77.80	$77.80
Purchase #5	$52.30	5.685%	$55.2733	$55.27	$55.25	$55.30
Purchase #6	$33.40	4.391%	$34.8666	$34.87	$34.85	$34.90
Purchase #7	$64.70	10.547%	$71.5239	$71.52	$71.50	$71.50
7 purchase totals =	$490.84		$523.0700	$523.07	$523.00	$523.10