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	$221.59	7.665%	$238.5749	$238.57	$238.55	$238.60
Purchase #2	$247.34	5.348%	$260.5677	$260.57	$260.55	$260.60
Purchase #3	$153.98	9.289%	$168.2832	$168.28	$168.30	$168.30
Purchase #4	$130.50	5.159%	$137.2325	$137.23	$137.25	$137.20
Purchase #5	$39.82	7.188%	$42.6823	$42.68	$42.70	$42.70
Purchase #6	$167.71	7.815%	$180.8165	$180.82	$180.80	$180.80
Purchase #7	$237.60	9.211%	$259.4853	$259.49	$259.50	$259.50
7 purchase totals =	$1,198.54		$1,287.6424	$1,287.64	$1,287.65	$1,287.70