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	$104.32	6.264%	$110.8546	$110.85	$110.85	$110.90
Purchase #2	$221.82	8.457%	$240.5793	$240.58	$240.60	$240.60
Purchase #3	$187.48	4.870%	$196.6103	$196.61	$196.60	$196.60
Purchase #4	$166.50	10.763%	$184.4204	$184.42	$184.40	$184.40
Purchase #5	$32.53	11.407%	$36.2407	$36.24	$36.25	$36.20
Purchase #6	$165.55	13.585%	$188.04	$188.04	$188.05	$188.00
Purchase #7	$139.71	6.829%	$149.2508	$149.25	$149.25	$149.30
7 purchase totals =	$1,017.91		$1,105.9961	$1,105.99	$1,106.00	$1,106.00