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	$174.52	9.521%	$191.136	$191.14	$191.15	$191.10
Purchase #2	$229.55	8.861%	$249.8904	$249.89	$249.90	$249.90
Purchase #3	$63.76	5.868%	$67.5014	$67.50	$67.50	$67.50
Purchase #4	$233.26	13.218%	$264.0923	$264.09	$264.10	$264.10
Purchase #5	$16.57	13.488%	$18.805	$18.81	$18.80	$18.80
Purchase #6	$198.91	6.691%	$212.2191	$212.22	$212.20	$212.20
Purchase #7	$132.89	12.509%	$149.5132	$149.51	$149.50	$149.50
7 purchase totals =	$1,049.46		$1,153.1574	$1,153.16	$1,153.15	$1,153.10