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	$180.54	7.544%	$194.1599	$194.16	$194.15	$194.20
Purchase #2	$40.99	8.579%	$44.5065	$44.51	$44.50	$44.50
Purchase #3	$181.56	5.321%	$191.2208	$191.22	$191.20	$191.20
Purchase #4	$41.53	9.602%	$45.5177	$45.52	$45.50	$45.50
Purchase #5	$89.28	12.110%	$100.0918	$100.09	$100.10	$100.10
Purchase #6	$93.62	10.556%	$103.5025	$103.50	$103.50	$103.50
Purchase #7	$9.56	6.143%	$10.1473	$10.15	$10.15	$10.10
7 purchase totals =	$637.08		$689.1465	$689.15	$689.10	$689.10