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	$153.75	6.103%	$163.1334	$163.13	$163.15	$163.10
Purchase #2	$18.50	7.798%	$19.9426	$19.94	$19.95	$19.90
Purchase #3	$62.92	6.540%	$67.035	$67.04	$67.05	$67.00
Purchase #4	$147.29	10.227%	$162.3533	$162.35	$162.35	$162.40
Purchase #5	$159.98	7.440%	$171.8825	$171.88	$171.90	$171.90
Purchase #6	$229.48	13.235%	$259.8517	$259.85	$259.85	$259.90
Purchase #7	$53.52	10.567%	$59.1755	$59.18	$59.20	$59.20
7 purchase totals =	$825.44		$903.3740	$903.37	$903.45	$903.40