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	$245.96	9.473%	$269.2598	$269.26	$269.25	$269.30
Purchase #2	$34.69	7.652%	$37.3445	$37.34	$37.35	$37.30
Purchase #3	$209.96	7.505%	$225.7175	$225.72	$225.70	$225.70
Purchase #4	$136.82	10.543%	$151.2449	$151.24	$151.25	$151.20
Purchase #5	$105.71	8.420%	$114.6108	$114.61	$114.60	$114.60
Purchase #6	$45.93	8.766%	$49.9562	$49.96	$49.95	$50.00
Purchase #7	$89.91	11.702%	$100.4313	$100.43	$100.45	$100.40
7 purchase totals =	$868.98		$948.5650	$948.56	$948.55	$948.50