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	$22.72	9.801%	$24.9468	$24.95	$24.95	$24.90
Purchase #2	$188.28	3.456%	$194.787	$194.79	$194.80	$194.80
Purchase #3	$225.25	13.433%	$255.5078	$255.51	$255.50	$255.50
Purchase #4	$27.96	12.637%	$31.4933	$31.49	$31.50	$31.50
Purchase #5	$129.62	13.607%	$147.2574	$147.26	$147.25	$147.30
Purchase #6	$208.72	7.667%	$224.7226	$224.72	$224.70	$224.70
Purchase #7	$194.32	11.110%	$215.909	$215.91	$215.90	$215.90
7 purchase totals =	$996.87		$1,094.6239	$1,094.63	$1,094.60	$1,094.60