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	$60.58	4.332%	$63.2043	$63.20	$63.20	$63.20
Purchase #2	$174.87	11.117%	$194.3103	$194.31	$194.30	$194.30
Purchase #3	$56.72	5.500%	$59.8396	$59.84	$59.85	$59.80
Purchase #4	$27.76	9.662%	$30.4422	$30.44	$30.45	$30.40
Purchase #5	$30.69	7.855%	$33.1007	$33.10	$33.10	$33.10
Purchase #6	$101.33	10.503%	$111.9727	$111.97	$111.95	$112.00
Purchase #7	$32.54	3.175%	$33.5731	$33.57	$33.55	$33.60
7 purchase totals =	$484.49		$526.4429	$526.43	$526.40	$526.40