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	$52.83	10.253%	$58.2467	$58.25	$58.25	$58.20
Purchase #2	$57.92	6.389%	$61.6205	$61.62	$61.60	$61.60
Purchase #3	$16.34	13.173%	$18.4925	$18.49	$18.50	$18.50
Purchase #4	$76.93	6.804%	$82.1643	$82.16	$82.15	$82.20
Purchase #5	$224.71	3.791%	$233.2288	$233.23	$233.25	$233.20
Purchase #6	$37.88	11.851%	$42.3692	$42.37	$42.35	$42.40
Purchase #7	$61.78	8.582%	$67.082	$67.08	$67.10	$67.10
7 purchase totals =	$528.39		$563.2040	$563.20	$563.20	$563.20