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	$102.59	3.120%	$105.7908	$105.79	$105.80	$105.80
Purchase #2	$243.52	11.791%	$272.2334	$272.23	$272.25	$272.20
Purchase #3	$164.98	9.435%	$180.5459	$180.55	$180.55	$180.50
Purchase #4	$68.49	4.407%	$71.5084	$71.51	$71.50	$71.50
Purchase #5	$232.70	9.653%	$255.1625	$255.16	$255.15	$255.20
Purchase #6	$67.54	8.339%	$73.1722	$73.17	$73.15	$73.20
Purchase #7	$131.51	13.166%	$148.8246	$148.82	$148.80	$148.80
7 purchase totals =	$1,011.33		$1,107.2378	$1,107.23	$1,107.20	$1,107.20