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	$148.44	6.389%	$157.9238	$157.92	$157.90	$157.90
Purchase #2	$108.25	13.736%	$123.1192	$123.12	$123.10	$123.10
Purchase #3	$53.56	4.226%	$55.8234	$55.82	$55.80	$55.80
Purchase #4	$116.83	7.765%	$125.9018	$125.90	$125.90	$125.90
Purchase #5	$111.92	3.797%	$116.1696	$116.17	$116.15	$116.20
Purchase #6	$155.42	7.269%	$166.7175	$166.72	$166.70	$166.70
Purchase #7	$17.56	4.353%	$18.3244	$18.32	$18.30	$18.30
7 purchase totals =	$711.98		$763.9797	$763.97	$763.85	$763.90