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	$52.54	6.312%	$55.8563	$55.86	$55.85	$55.90
Purchase #2	$78.74	4.588%	$82.3526	$82.35	$82.35	$82.40
Purchase #3	$37.51	11.186%	$41.7059	$41.71	$41.70	$41.70
Purchase #4	$169.56	13.824%	$193	$193.00	$193.00	$193.00
Purchase #5	$227.49	13.868%	$259.0383	$259.04	$259.05	$259.00
Purchase #6	$220.53	3.862%	$229.0469	$229.05	$229.05	$229.00
Purchase #7	$149.76	9.836%	$164.4904	$164.49	$164.50	$164.50
7 purchase totals =	$936.13		$1,025.4904	$1,025.50	$1,025.50	$1,025.50