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	$50.92	3.624%	$52.7653	$52.77	$52.75	$52.80
Purchase #2	$89.43	11.267%	$99.5061	$99.51	$99.50	$99.50
Purchase #3	$93.71	11.498%	$104.4848	$104.48	$104.50	$104.50
Purchase #4	$87.71	13.658%	$99.6894	$99.69	$99.70	$99.70
Purchase #5	$198.34	9.774%	$217.7258	$217.73	$217.75	$217.70
Purchase #6	$240.69	12.817%	$271.5392	$271.54	$271.55	$271.50
Purchase #7	$81.84	4.377%	$85.4221	$85.42	$85.40	$85.40
7 purchase totals =	$842.64		$931.1327	$931.14	$931.15	$931.10