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	$36.72	10.142%	$40.4441	$40.44	$40.45	$40.40
Purchase #2	$11.43	4.132%	$11.9023	$11.90	$11.90	$11.90
Purchase #3	$28.43	5.222%	$29.9146	$29.91	$29.90	$29.90
Purchase #4	$5.82	6.497%	$6.1981	$6.20	$6.20	$6.20
Purchase #5	$41.87	9.487%	$45.8422	$45.84	$45.85	$45.80
Purchase #6	$137.25	11.203%	$152.6261	$152.63	$152.65	$152.60
Purchase #7	$108.69	9.616%	$119.1416	$119.14	$119.15	$119.10
7 purchase totals =	$370.21		$406.0690	$406.06	$406.10	$405.90