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	$33.33	6.547%	$35.5121	$35.51	$35.50	$35.50
Purchase #2	$166.52	11.191%	$185.1553	$185.16	$185.15	$185.20
Purchase #3	$10.58	4.589%	$11.0655	$11.07	$11.05	$11.10
Purchase #4	$164.29	11.194%	$182.6806	$182.68	$182.70	$182.70
Purchase #5	$181.43	6.112%	$192.519	$192.52	$192.50	$192.50
Purchase #6	$225.72	3.639%	$233.934	$233.93	$233.95	$233.90
Purchase #7	$250.69	9.560%	$274.656	$274.66	$274.65	$274.70
7 purchase totals =	$1,032.56		$1,115.5225	$1,115.53	$1,115.50	$1,115.60