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	$228.95	9.361%	$250.382	$250.38	$250.40	$250.40
Purchase #2	$97.58	13.188%	$110.4489	$110.45	$110.45	$110.40
Purchase #3	$38.64	12.635%	$43.5222	$43.52	$43.50	$43.50
Purchase #4	$188.72	6.231%	$200.4791	$200.48	$200.50	$200.50
Purchase #5	$125.57	6.537%	$133.7785	$133.78	$133.80	$133.80
Purchase #6	$178.89	6.106%	$189.813	$189.81	$189.80	$189.80
Purchase #7	$85.56	13.466%	$97.0815	$97.08	$97.10	$97.10
7 purchase totals =	$943.91		$1,025.5052	$1,025.50	$1,025.55	$1,025.50