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	$57.72	7.201%	$61.8764	$61.88	$61.90	$61.90
Purchase #2	$69.89	8.454%	$75.7985	$75.80	$75.80	$75.80
Purchase #3	$82.62	3.515%	$85.5241	$85.52	$85.50	$85.50
Purchase #4	$81.49	4.456%	$85.1212	$85.12	$85.10	$85.10
Purchase #5	$172.46	13.167%	$195.1678	$195.17	$195.15	$195.20
Purchase #6	$19.72	7.144%	$21.1288	$21.13	$21.15	$21.10
Purchase #7	$56.46	8.456%	$61.2343	$61.23	$61.25	$61.20
7 purchase totals =	$540.36		$585.8511	$585.85	$585.85	$585.80