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	$217.39	12.482%	$244.5246	$244.52	$244.50	$244.50
Purchase #2	$153.65	10.300%	$169.476	$169.48	$169.50	$169.50
Purchase #3	$134.79	9.821%	$148.0277	$148.03	$148.05	$148.00
Purchase #4	$80.91	5.528%	$85.3827	$85.38	$85.40	$85.40
Purchase #5	$233.52	8.506%	$253.3832	$253.38	$253.40	$253.40
Purchase #6	$88.43	12.751%	$99.7057	$99.71	$99.70	$99.70
Purchase #7	$34.52	4.176%	$35.9616	$35.96	$35.95	$36.00
7 purchase totals =	$943.21		$1,036.4615	$1,036.46	$1,036.50	$1,036.50