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	$93.95	10.510%	$103.8241	$103.82	$103.80	$103.80
Purchase #2	$132.67	13.766%	$150.9334	$150.93	$150.95	$150.90
Purchase #3	$44.52	4.112%	$46.3507	$46.35	$46.35	$46.40
Purchase #4	$134.70	5.442%	$142.0304	$142.03	$142.05	$142.00
Purchase #5	$78.54	4.545%	$82.1096	$82.11	$82.10	$82.10
Purchase #6	$178.65	8.579%	$193.9764	$193.98	$194.00	$194.00
Purchase #7	$240.96	13.827%	$274.2775	$274.28	$274.30	$274.30
7 purchase totals =	$903.99		$993.5021	$993.50	$993.55	$993.50