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	$199.38	5.260%	$209.8674	$209.87	$209.85	$209.90
Purchase #2	$244.90	12.515%	$275.5492	$275.55	$275.55	$275.50
Purchase #3	$240.81	12.640%	$271.2484	$271.25	$271.25	$271.20
Purchase #4	$142.36	12.816%	$160.6049	$160.60	$160.60	$160.60
Purchase #5	$29.46	13.485%	$33.4327	$33.43	$33.45	$33.40
Purchase #6	$225.80	7.460%	$242.6447	$242.64	$242.65	$242.60
Purchase #7	$216.79	10.221%	$238.9481	$238.95	$238.95	$238.90
7 purchase totals =	$1,299.50		$1,432.2954	$1,432.29	$1,432.30	$1,432.10