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	$73.31	3.772%	$76.0753	$76.08	$76.10	$76.10
Purchase #2	$5.34	5.114%	$5.6131	$5.61	$5.60	$5.60
Purchase #3	$151.31	4.740%	$158.4821	$158.48	$158.50	$158.50
Purchase #4	$157.32	10.293%	$173.5129	$173.51	$173.50	$173.50
Purchase #5	$5.90	7.192%	$6.3243	$6.32	$6.30	$6.30
Purchase #6	$68.43	12.627%	$77.0707	$77.07	$77.05	$77.10
Purchase #7	$91.69	11.125%	$101.8905	$101.89	$101.90	$101.90
7 purchase totals =	$553.30		$598.9689	$598.96	$598.95	$599.00