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	$89.25	11.413%	$99.4361	$99.44	$99.45	$99.40
Purchase #2	$82.41	8.335%	$89.2789	$89.28	$89.30	$89.30
Purchase #3	$45.27	4.410%	$47.2664	$47.27	$47.25	$47.30
Purchase #4	$247.61	11.756%	$276.719	$276.72	$276.70	$276.70
Purchase #5	$123.60	12.864%	$139.4999	$139.50	$139.50	$139.50
Purchase #6	$198.83	11.169%	$221.0373	$221.04	$221.05	$221.00
Purchase #7	$25.32	11.705%	$28.2837	$28.28	$28.30	$28.30
7 purchase totals =	$812.29		$901.5213	$901.53	$901.55	$901.50