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	$78.71	5.355%	$82.9249	$82.92	$82.90	$82.90
Purchase #2	$250.80	12.864%	$283.0629	$283.06	$283.05	$283.10
Purchase #3	$88.53	3.481%	$91.6117	$91.61	$91.60	$91.60
Purchase #4	$39.82	8.681%	$43.2768	$43.28	$43.30	$43.30
Purchase #5	$212.73	7.465%	$228.6103	$228.61	$228.60	$228.60
Purchase #6	$126.68	13.429%	$143.6919	$143.69	$143.70	$143.70
Purchase #7	$161.84	11.119%	$179.835	$179.84	$179.85	$179.80
7 purchase totals =	$959.11		$1,053.0135	$1,053.01	$1,053.00	$1,053.00