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	$162.82	11.679%	$181.8357	$181.84	$181.85	$181.80
Purchase #2	$52.49	10.739%	$58.1269	$58.13	$58.15	$58.10
Purchase #3	$209.25	6.226%	$222.2779	$222.28	$222.30	$222.30
Purchase #4	$106.92	12.146%	$119.9065	$119.91	$119.90	$119.90
Purchase #5	$206.94	5.176%	$217.6512	$217.65	$217.65	$217.70
Purchase #6	$91.46	4.848%	$95.894	$95.89	$95.90	$95.90
Purchase #7	$224.25	13.731%	$255.0418	$255.04	$255.05	$255.00
7 purchase totals =	$1,054.13		$1,150.7340	$1,150.74	$1,150.80	$1,150.70