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	$29.56	10.266%	$32.5946	$32.59	$32.60	$32.60
Purchase #2	$106.75	4.837%	$111.9135	$111.91	$111.90	$111.90
Purchase #3	$86.34	4.357%	$90.1018	$90.10	$90.10	$90.10
Purchase #4	$28.84	12.333%	$32.3968	$32.40	$32.40	$32.40
Purchase #5	$175.97	3.870%	$182.78	$182.78	$182.80	$182.80
Purchase #6	$89.87	10.717%	$99.5014	$99.50	$99.50	$99.50
Purchase #7	$74.33	3.634%	$77.0312	$77.03	$77.05	$77.00
7 purchase totals =	$591.66		$626.3193	$626.31	$626.35	$626.30