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	$186.73	7.565%	$200.8561	$200.86	$200.85	$200.90
Purchase #2	$42.76	4.579%	$44.718	$44.72	$44.70	$44.70
Purchase #3	$239.67	4.604%	$250.7044	$250.70	$250.70	$250.70
Purchase #4	$77.37	8.474%	$83.9263	$83.93	$83.95	$83.90
Purchase #5	$173.81	3.360%	$179.65	$179.65	$179.65	$179.70
Purchase #6	$65.54	11.767%	$73.2521	$73.25	$73.25	$73.30
Purchase #7	$10.32	4.840%	$10.8195	$10.82	$10.80	$10.80
7 purchase totals =	$796.20		$843.9264	$843.93	$843.90	$844.00