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	$92.91	8.590%	$100.891	$100.89	$100.90	$100.90
Purchase #2	$244.39	3.255%	$252.3449	$252.34	$252.35	$252.30
Purchase #3	$231.80	4.109%	$241.3247	$241.32	$241.30	$241.30
Purchase #4	$230.62	5.200%	$242.6122	$242.61	$242.60	$242.60
Purchase #5	$99.81	12.407%	$112.1934	$112.19	$112.20	$112.20
Purchase #6	$73.54	11.688%	$82.1354	$82.14	$82.15	$82.10
Purchase #7	$30.91	3.369%	$31.9514	$31.95	$31.95	$32.00
7 purchase totals =	$1,003.98		$1,063.4530	$1,063.44	$1,063.45	$1,063.40