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	$116.65	5.473%	$123.0343	$123.03	$123.05	$123.00
Purchase #2	$82.45	6.149%	$87.5199	$87.52	$87.50	$87.50
Purchase #3	$145.57	4.633%	$152.3143	$152.31	$152.30	$152.30
Purchase #4	$204.53	12.586%	$230.2721	$230.27	$230.25	$230.30
Purchase #5	$51.67	4.375%	$53.9306	$53.93	$53.95	$53.90
Purchase #6	$154.92	6.811%	$165.4716	$165.47	$165.45	$165.50
Purchase #7	$104.72	10.222%	$115.4245	$115.42	$115.40	$115.40
7 purchase totals =	$860.51		$927.9673	$927.95	$927.90	$927.90