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	$125.33	7.306%	$134.4866	$134.49	$134.50	$134.50
Purchase #2	$67.92	6.713%	$72.4795	$72.48	$72.50	$72.50
Purchase #3	$38.90	3.378%	$40.214	$40.21	$40.20	$40.20
Purchase #4	$52.43	7.492%	$56.3581	$56.36	$56.35	$56.40
Purchase #5	$201.70	5.245%	$212.2792	$212.28	$212.30	$212.30
Purchase #6	$72.26	6.869%	$77.2235	$77.22	$77.20	$77.20
Purchase #7	$12.83	13.191%	$14.5224	$14.52	$14.50	$14.50
7 purchase totals =	$571.37		$607.5633	$607.56	$607.55	$607.60