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	$179.81	9.375%	$196.6672	$196.67	$196.65	$196.70
Purchase #2	$51.84	13.274%	$58.7212	$58.72	$58.70	$58.70
Purchase #3	$243.56	6.738%	$259.9711	$259.97	$259.95	$260.00
Purchase #4	$151.38	11.104%	$168.1892	$168.19	$168.20	$168.20
Purchase #5	$250.38	5.794%	$264.887	$264.89	$264.90	$264.90
Purchase #6	$25.48	10.714%	$28.2099	$28.21	$28.20	$28.20
Purchase #7	$157.79	11.788%	$176.3903	$176.39	$176.40	$176.40
7 purchase totals =	$1,060.24		$1,153.0359	$1,153.04	$1,153.00	$1,153.10