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	$138.82	11.142%	$154.2873	$154.29	$154.30	$154.30
Purchase #2	$124.61	4.626%	$130.3745	$130.37	$130.35	$130.40
Purchase #3	$49.34	10.238%	$54.3914	$54.39	$54.40	$54.40
Purchase #4	$198.96	10.332%	$219.5165	$219.52	$219.50	$219.50
Purchase #5	$186.88	5.224%	$196.6426	$196.64	$196.65	$196.60
Purchase #6	$242.45	13.484%	$275.142	$275.14	$275.15	$275.10
Purchase #7	$209.32	5.432%	$220.6903	$220.69	$220.70	$220.70
7 purchase totals =	$1,150.38		$1,251.0446	$1,251.04	$1,251.05	$1,251.00