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	$183.53	9.110%	$200.2496	$200.25	$200.25	$200.20
Purchase #2	$16.89	9.114%	$18.4294	$18.43	$18.45	$18.40
Purchase #3	$19.64	5.165%	$20.6544	$20.65	$20.65	$20.70
Purchase #4	$70.74	11.225%	$78.6806	$78.68	$78.70	$78.70
Purchase #5	$41.89	6.538%	$44.6288	$44.63	$44.65	$44.60
Purchase #6	$92.72	6.230%	$98.4965	$98.50	$98.50	$98.50
Purchase #7	$15.42	6.124%	$16.3643	$16.36	$16.35	$16.40
7 purchase totals =	$440.83		$477.5036	$477.50	$477.55	$477.50