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	$83.55	7.233%	$89.5932	$89.59	$89.60	$89.60
Purchase #2	$224.45	8.357%	$243.2073	$243.21	$243.20	$243.20
Purchase #3	$99.69	3.763%	$103.4413	$103.44	$103.45	$103.40
Purchase #4	$197.43	7.780%	$212.7901	$212.79	$212.80	$212.80
Purchase #5	$11.49	8.352%	$12.4496	$12.45	$12.45	$12.40
Purchase #6	$191.32	10.321%	$211.0661	$211.07	$211.05	$211.10
Purchase #7	$154.86	6.689%	$165.2186	$165.22	$165.20	$165.20
7 purchase totals =	$962.79		$1,037.7662	$1,037.77	$1,037.75	$1,037.70