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	$163.40	7.234%	$175.2204	$175.22	$175.20	$175.20
Purchase #2	$152.93	7.323%	$164.1291	$164.13	$164.15	$164.10
Purchase #3	$146.50	9.575%	$160.5274	$160.53	$160.55	$160.50
Purchase #4	$90.29	9.846%	$99.18	$99.18	$99.20	$99.20
Purchase #5	$222.54	11.372%	$247.8472	$247.85	$247.85	$247.80
Purchase #6	$38.83	8.853%	$42.2676	$42.27	$42.25	$42.30
Purchase #7	$107.63	12.358%	$120.9309	$120.93	$120.95	$120.90
7 purchase totals =	$922.12		$1,010.1026	$1,010.11	$1,010.15	$1,010.00