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	$168.48	13.183%	$190.6907	$190.69	$190.70	$190.70
Purchase #2	$213.89	10.314%	$235.9506	$235.95	$235.95	$236.00
Purchase #3	$89.95	11.679%	$100.4553	$100.46	$100.45	$100.50
Purchase #4	$222.56	4.400%	$232.3526	$232.35	$232.35	$232.40
Purchase #5	$53.30	11.819%	$59.5995	$59.60	$59.60	$59.60
Purchase #6	$34.88	6.742%	$37.2316	$37.23	$37.25	$37.20
Purchase #7	$110.88	10.316%	$122.3184	$122.32	$122.30	$122.30
7 purchase totals =	$893.94		$978.5987	$978.60	$978.60	$978.70