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	$148.35	7.793%	$159.9109	$159.91	$159.90	$159.90
Purchase #2	$137.83	3.464%	$142.6044	$142.60	$142.60	$142.60
Purchase #3	$123.38	12.334%	$138.5977	$138.60	$138.60	$138.60
Purchase #4	$230.41	4.215%	$240.1218	$240.12	$240.10	$240.10
Purchase #5	$142.82	6.344%	$151.8805	$151.88	$151.90	$151.90
Purchase #6	$136.70	7.415%	$146.8363	$146.84	$146.85	$146.80
Purchase #7	$92.45	10.502%	$102.1591	$102.16	$102.15	$102.20
7 purchase totals =	$1,011.94		$1,082.1107	$1,082.11	$1,082.10	$1,082.10