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	$141.82	9.456%	$155.2305	$155.23	$155.25	$155.20
Purchase #2	$60.84	4.220%	$63.4074	$63.41	$63.40	$63.40
Purchase #3	$20.99	13.506%	$23.8249	$23.82	$23.80	$23.80
Purchase #4	$45.55	11.274%	$50.6853	$50.69	$50.70	$50.70
Purchase #5	$208.47	3.210%	$215.1619	$215.16	$215.15	$215.20
Purchase #6	$175.41	5.758%	$185.5101	$185.51	$185.50	$185.50
Purchase #7	$55.78	6.116%	$59.1915	$59.19	$59.20	$59.20
7 purchase totals =	$708.86		$753.0116	$753.01	$753.00	$753.00