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	$136.26	8.536%	$147.8912	$147.89	$147.90	$147.90
Purchase #2	$126.98	13.584%	$144.229	$144.23	$144.25	$144.20
Purchase #3	$199.57	10.123%	$219.7725	$219.77	$219.75	$219.80
Purchase #4	$169.72	6.611%	$180.9402	$180.94	$180.95	$180.90
Purchase #5	$32.91	13.246%	$37.2693	$37.27	$37.25	$37.30
Purchase #6	$120.75	8.316%	$130.7916	$130.79	$130.80	$130.80
Purchase #7	$144.26	4.174%	$150.2814	$150.28	$150.30	$150.30
7 purchase totals =	$930.45		$1,011.1752	$1,011.17	$1,011.20	$1,011.20