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	$231.88	12.425%	$260.6911	$260.69	$260.70	$260.70
Purchase #2	$90.86	3.618%	$94.1473	$94.15	$94.15	$94.10
Purchase #3	$142.41	6.676%	$151.9173	$151.92	$151.90	$151.90
Purchase #4	$29.97	11.544%	$33.4297	$33.43	$33.45	$33.40
Purchase #5	$97.56	8.427%	$105.7814	$105.78	$105.80	$105.80
Purchase #6	$157.57	13.691%	$179.1429	$179.14	$179.15	$179.10
Purchase #7	$47.50	13.677%	$53.9966	$54.00	$54.00	$54.00
7 purchase totals =	$797.75		$879.1063	$879.11	$879.15	$879.00