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	$114.68	10.224%	$126.4049	$126.40	$126.40	$126.40
Purchase #2	$150.61	9.531%	$164.9646	$164.96	$164.95	$165.00
Purchase #3	$64.56	11.362%	$71.8953	$71.90	$71.90	$71.90
Purchase #4	$139.32	8.760%	$151.5244	$151.52	$151.50	$151.50
Purchase #5	$84.84	6.797%	$90.6066	$90.61	$90.60	$90.60
Purchase #6	$33.41	6.303%	$35.5158	$35.52	$35.50	$35.50
Purchase #7	$248.98	6.274%	$264.601	$264.60	$264.60	$264.60
7 purchase totals =	$836.40		$905.5126	$905.51	$905.45	$905.50