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	$65.57	9.149%	$71.569	$71.57	$71.55	$71.60
Purchase #2	$105.43	5.467%	$111.1939	$111.19	$111.20	$111.20
Purchase #3	$130.72	7.750%	$140.8508	$140.85	$140.85	$140.90
Purchase #4	$98.42	7.852%	$106.1479	$106.15	$106.15	$106.10
Purchase #5	$131.97	11.646%	$147.3392	$147.34	$147.35	$147.30
Purchase #6	$219.64	13.836%	$250.0294	$250.03	$250.05	$250.00
Purchase #7	$10.98	13.664%	$12.4803	$12.48	$12.50	$12.50
7 purchase totals =	$762.73		$839.6105	$839.61	$839.65	$839.60