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	$86.96	8.287%	$94.1664	$94.17	$94.15	$94.20
Purchase #2	$21.25	7.361%	$22.8142	$22.81	$22.80	$22.80
Purchase #3	$38.30	10.729%	$42.4092	$42.41	$42.40	$42.40
Purchase #4	$238.90	12.152%	$267.9311	$267.93	$267.95	$267.90
Purchase #5	$12.47	10.371%	$13.7633	$13.76	$13.75	$13.80
Purchase #6	$159.87	12.485%	$179.8298	$179.83	$179.85	$179.80
Purchase #7	$125.39	11.361%	$139.6356	$139.64	$139.65	$139.60
7 purchase totals =	$683.14		$760.5496	$760.55	$760.55	$760.50