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	$57.62	3.482%	$59.6263	$59.63	$59.65	$59.60
Purchase #2	$30.89	10.776%	$34.2187	$34.22	$34.20	$34.20
Purchase #3	$188.55	9.139%	$205.7816	$205.78	$205.80	$205.80
Purchase #4	$109.93	10.340%	$121.2968	$121.30	$121.30	$121.30
Purchase #5	$190.31	4.405%	$198.6932	$198.69	$198.70	$198.70
Purchase #6	$71.62	9.436%	$78.3781	$78.38	$78.40	$78.40
Purchase #7	$85.77	13.478%	$97.3301	$97.33	$97.35	$97.30
7 purchase totals =	$734.69		$795.3248	$795.33	$795.40	$795.30