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	$47.47	5.592%	$50.1245	$50.12	$50.10	$50.10
Purchase #2	$40.31	8.681%	$43.8093	$43.81	$43.80	$43.80
Purchase #3	$191.29	13.835%	$217.755	$217.76	$217.75	$217.80
Purchase #4	$212.46	7.374%	$228.1268	$228.13	$228.15	$228.10
Purchase #5	$219.86	11.425%	$244.979	$244.98	$245.00	$245.00
Purchase #6	$229.57	4.799%	$240.5871	$240.59	$240.60	$240.60
Purchase #7	$70.82	6.694%	$75.5607	$75.56	$75.55	$75.60
7 purchase totals =	$1,011.78		$1,100.9424	$1,100.95	$1,100.95	$1,101.00