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	$95.43	11.291%	$106.205	$106.21	$106.20	$106.20
Purchase #2	$83.92	13.395%	$95.1611	$95.16	$95.15	$95.20
Purchase #3	$206.85	10.352%	$228.2631	$228.26	$228.25	$228.30
Purchase #4	$249.82	11.525%	$278.6118	$278.61	$278.60	$278.60
Purchase #5	$31.52	12.751%	$35.5391	$35.54	$35.55	$35.50
Purchase #6	$37.89	12.191%	$42.5092	$42.51	$42.50	$42.50
Purchase #7	$146.69	13.661%	$166.7293	$166.73	$166.75	$166.70
7 purchase totals =	$852.12		$953.0186	$953.02	$953.00	$953.00