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	$203.40	6.474%	$216.5681	$216.57	$216.55	$216.60
Purchase #2	$67.43	4.356%	$70.3673	$70.37	$70.35	$70.40
Purchase #3	$195.80	8.754%	$212.9403	$212.94	$212.95	$212.90
Purchase #4	$101.29	8.355%	$109.7528	$109.75	$109.75	$109.80
Purchase #5	$118.39	4.502%	$123.7199	$123.72	$123.70	$123.70
Purchase #6	$213.59	4.624%	$223.4664	$223.47	$223.45	$223.50
Purchase #7	$216.76	6.292%	$230.3985	$230.40	$230.40	$230.40
7 purchase totals =	$1,116.66		$1,187.2133	$1,187.22	$1,187.15	$1,187.30