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	$73.51	4.564%	$76.865	$76.87	$76.85	$76.90
Purchase #2	$81.91	4.756%	$85.8056	$85.81	$85.80	$85.80
Purchase #3	$137.93	10.427%	$152.312	$152.31	$152.30	$152.30
Purchase #4	$56.90	7.819%	$61.349	$61.35	$61.35	$61.30
Purchase #5	$153.54	8.473%	$166.5494	$166.55	$166.55	$166.50
Purchase #6	$223.25	7.208%	$239.3419	$239.34	$239.35	$239.30
Purchase #7	$229.48	13.388%	$260.2028	$260.20	$260.20	$260.20
7 purchase totals =	$956.52		$1,042.4257	$1,042.43	$1,042.40	$1,042.30