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	$229.89	4.679%	$240.6466	$240.65	$240.65	$240.60
Purchase #2	$204.73	8.812%	$222.7708	$222.77	$222.75	$222.80
Purchase #3	$248.40	4.225%	$258.8949	$258.89	$258.90	$258.90
Purchase #4	$91.51	8.183%	$98.9983	$99.00	$99.00	$99.00
Purchase #5	$54.45	6.166%	$57.8074	$57.81	$57.80	$57.80
Purchase #6	$137.88	12.533%	$155.1605	$155.16	$155.15	$155.20
Purchase #7	$45.82	4.469%	$47.8677	$47.87	$47.85	$47.90
7 purchase totals =	$1,012.68		$1,082.1462	$1,082.15	$1,082.10	$1,082.20