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	$113.42	9.450%	$124.1382	$124.14	$124.15	$124.10
Purchase #2	$183.47	13.386%	$208.0293	$208.03	$208.05	$208.00
Purchase #3	$81.51	5.329%	$85.8537	$85.85	$85.85	$85.90
Purchase #4	$65.82	6.611%	$70.1714	$70.17	$70.15	$70.20
Purchase #5	$151.41	12.645%	$170.5558	$170.56	$170.55	$170.60
Purchase #6	$155.39	10.795%	$172.1644	$172.16	$172.15	$172.20
Purchase #7	$28.63	9.371%	$31.3129	$31.31	$31.30	$31.30
7 purchase totals =	$779.65		$862.2257	$862.22	$862.20	$862.30