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	$95.54	3.767%	$99.139	$99.14	$99.15	$99.10
Purchase #2	$229.58	7.517%	$246.8375	$246.84	$246.85	$246.80
Purchase #3	$66.82	7.590%	$71.8916	$71.89	$71.90	$71.90
Purchase #4	$31.69	3.460%	$32.7865	$32.79	$32.80	$32.80
Purchase #5	$84.91	12.384%	$95.4253	$95.43	$95.45	$95.40
Purchase #6	$223.44	13.212%	$252.9609	$252.96	$252.95	$253.00
Purchase #7	$235.35	7.728%	$253.5378	$253.54	$253.55	$253.50
7 purchase totals =	$967.33		$1,052.5786	$1,052.59	$1,052.65	$1,052.50