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	$203.59	10.303%	$224.5659	$224.57	$224.55	$224.60
Purchase #2	$205.51	10.520%	$227.1297	$227.13	$227.15	$227.10
Purchase #3	$42.55	8.123%	$46.0063	$46.01	$46.00	$46.00
Purchase #4	$102.25	13.769%	$116.3288	$116.33	$116.35	$116.30
Purchase #5	$55.46	13.568%	$62.9848	$62.98	$63.00	$63.00
Purchase #6	$79.81	7.552%	$85.8373	$85.84	$85.85	$85.80
Purchase #7	$99.99	11.715%	$111.7038	$111.70	$111.70	$111.70
7 purchase totals =	$789.16		$874.5566	$874.56	$874.60	$874.50