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	$110.59	4.389%	$115.4438	$115.44	$115.45	$115.40
Purchase #2	$68.40	11.628%	$76.3536	$76.35	$76.35	$76.40
Purchase #3	$101.95	10.748%	$112.9076	$112.91	$112.90	$112.90
Purchase #4	$90.45	9.603%	$99.1359	$99.14	$99.15	$99.10
Purchase #5	$234.56	12.682%	$264.3069	$264.31	$264.30	$264.30
Purchase #6	$112.88	5.648%	$119.2555	$119.26	$119.25	$119.30
Purchase #7	$242.71	13.731%	$276.0365	$276.04	$276.05	$276.00
7 purchase totals =	$961.54		$1,063.4398	$1,063.45	$1,063.45	$1,063.40