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	$72.98	5.142%	$76.7326	$76.73	$76.75	$76.70
Purchase #2	$131.81	9.376%	$144.1685	$144.17	$144.15	$144.20
Purchase #3	$78.46	13.716%	$89.2216	$89.22	$89.20	$89.20
Purchase #4	$120.80	13.542%	$137.1587	$137.16	$137.15	$137.20
Purchase #5	$218.98	5.617%	$231.2801	$231.28	$231.30	$231.30
Purchase #6	$56.32	9.190%	$61.4958	$61.50	$61.50	$61.50
Purchase #7	$183.68	11.539%	$204.8748	$204.87	$204.85	$204.90
7 purchase totals =	$863.03		$944.9321	$944.93	$944.90	$945.00