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	$149.85	6.584%	$159.7161	$159.72	$159.70	$159.70
Purchase #2	$67.45	6.676%	$71.953	$71.95	$71.95	$72.00
Purchase #3	$32.49	6.234%	$34.5154	$34.52	$34.50	$34.50
Purchase #4	$20.98	3.387%	$21.6906	$21.69	$21.70	$21.70
Purchase #5	$196.72	11.700%	$219.7362	$219.74	$219.75	$219.70
Purchase #6	$87.59	12.477%	$98.5186	$98.52	$98.50	$98.50
Purchase #7	$37.74	12.530%	$42.4688	$42.47	$42.45	$42.50
7 purchase totals =	$592.82		$648.5987	$648.61	$648.55	$648.60