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	$130.87	13.421%	$148.4341	$148.43	$148.45	$148.40
Purchase #2	$99.76	6.204%	$105.9491	$105.95	$105.95	$105.90
Purchase #3	$97.79	7.810%	$105.4274	$105.43	$105.45	$105.40
Purchase #4	$72.44	12.141%	$81.2349	$81.23	$81.25	$81.20
Purchase #5	$200.69	12.528%	$225.8324	$225.83	$225.85	$225.80
Purchase #6	$18.31	6.496%	$19.4994	$19.50	$19.50	$19.50
Purchase #7	$47.98	10.432%	$52.9853	$52.99	$53.00	$53.00
7 purchase totals =	$667.84		$739.3626	$739.36	$739.45	$739.20