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	$247.75	4.630%	$259.2208	$259.22	$259.20	$259.20
Purchase #2	$232.60	4.631%	$243.3717	$243.37	$243.35	$243.40
Purchase #3	$202.98	9.828%	$222.9289	$222.93	$222.95	$222.90
Purchase #4	$97.57	11.531%	$108.8208	$108.82	$108.80	$108.80
Purchase #5	$141.37	3.103%	$145.7567	$145.76	$145.75	$145.80
Purchase #6	$62.92	8.754%	$68.428	$68.43	$68.45	$68.40
Purchase #7	$137.64	10.343%	$151.8761	$151.88	$151.90	$151.90
7 purchase totals =	$1,122.83		$1,200.4030	$1,200.41	$1,200.40	$1,200.40