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	$128.31	11.845%	$143.5083	$143.51	$143.50	$143.50
Purchase #2	$67.62	13.178%	$76.531	$76.53	$76.55	$76.50
Purchase #3	$99.92	6.558%	$106.4728	$106.47	$106.45	$106.50
Purchase #4	$147.66	10.113%	$162.5929	$162.59	$162.60	$162.60
Purchase #5	$213.75	4.871%	$224.1618	$224.16	$224.15	$224.20
Purchase #6	$165.64	11.434%	$184.5793	$184.58	$184.60	$184.60
Purchase #7	$10.46	9.550%	$11.4589	$11.46	$11.45	$11.50
7 purchase totals =	$833.36		$909.3050	$909.30	$909.30	$909.40