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	$169.92	13.163%	$192.2866	$192.29	$192.30	$192.30
Purchase #2	$186.72	12.228%	$209.5521	$209.55	$209.55	$209.60
Purchase #3	$127.61	6.609%	$136.0437	$136.04	$136.05	$136.00
Purchase #4	$186.92	4.283%	$194.9258	$194.93	$194.95	$194.90
Purchase #5	$185.27	3.495%	$191.7452	$191.75	$191.75	$191.70
Purchase #6	$61.35	10.526%	$67.8077	$67.81	$67.80	$67.80
Purchase #7	$42.50	7.317%	$45.6097	$45.61	$45.60	$45.60
7 purchase totals =	$960.29		$1,037.9708	$1,037.98	$1,038.00	$1,037.90