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	$50.33	7.806%	$54.2588	$54.26	$54.25	$54.30
Purchase #2	$86.34	7.711%	$92.9977	$93.00	$93.00	$93.00
Purchase #3	$92.86	7.825%	$100.1263	$100.13	$100.15	$100.10
Purchase #4	$237.62	5.298%	$250.2091	$250.21	$250.20	$250.20
Purchase #5	$100.65	4.212%	$104.8894	$104.89	$104.90	$104.90
Purchase #6	$116.29	13.104%	$131.5286	$131.53	$131.55	$131.50
Purchase #7	$250.80	7.320%	$269.1586	$269.16	$269.15	$269.20
7 purchase totals =	$934.89		$1,003.1685	$1,003.18	$1,003.20	$1,003.20