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	$190.33	3.408%	$196.8164	$196.82	$196.80	$196.80
Purchase #2	$205.86	11.122%	$228.7557	$228.76	$228.75	$228.80
Purchase #3	$138.27	10.299%	$152.5104	$152.51	$152.50	$152.50
Purchase #4	$209.93	7.341%	$225.341	$225.34	$225.35	$225.30
Purchase #5	$222.47	9.761%	$244.1853	$244.19	$244.20	$244.20
Purchase #6	$57.85	11.280%	$64.3755	$64.38	$64.40	$64.40
Purchase #7	$215.44	3.702%	$223.4156	$223.42	$223.40	$223.40
7 purchase totals =	$1,240.15		$1,335.3999	$1,335.42	$1,335.40	$1,335.40