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	$55.30	12.739%	$62.3447	$62.34	$62.35	$62.30
Purchase #2	$77.54	11.430%	$86.4028	$86.40	$86.40	$86.40
Purchase #3	$162.43	6.108%	$172.3512	$172.35	$172.35	$172.40
Purchase #4	$56.98	11.387%	$63.4683	$63.47	$63.45	$63.50
Purchase #5	$29.84	13.158%	$33.7663	$33.77	$33.75	$33.80
Purchase #6	$192.29	10.454%	$212.392	$212.39	$212.40	$212.40
Purchase #7	$96.78	12.639%	$109.012	$109.01	$109.00	$109.00
7 purchase totals =	$671.16		$739.7373	$739.73	$739.70	$739.80