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	$69.31	3.542%	$71.765	$71.77	$71.75	$71.80
Purchase #2	$92.37	7.437%	$99.2396	$99.24	$99.25	$99.20
Purchase #3	$120.71	6.453%	$128.4994	$128.50	$128.50	$128.50
Purchase #4	$137.97	7.414%	$148.1991	$148.20	$148.20	$148.20
Purchase #5	$41.81	12.733%	$47.1337	$47.13	$47.15	$47.10
Purchase #6	$70.52	12.347%	$79.2271	$79.23	$79.25	$79.20
Purchase #7	$78.28	5.341%	$82.4609	$82.46	$82.45	$82.50
7 purchase totals =	$610.97		$656.5248	$656.53	$656.55	$656.50