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	$180.34	5.478%	$190.219	$190.22	$190.20	$190.20
Purchase #2	$235.77	8.502%	$255.8152	$255.82	$255.80	$255.80
Purchase #3	$140.27	6.187%	$148.9485	$148.95	$148.95	$148.90
Purchase #4	$104.90	13.252%	$118.8013	$118.80	$118.80	$118.80
Purchase #5	$20.49	5.234%	$21.5624	$21.56	$21.55	$21.60
Purchase #6	$95.82	9.545%	$104.966	$104.97	$104.95	$105.00
Purchase #7	$85.33	7.646%	$91.8543	$91.85	$91.85	$91.90
7 purchase totals =	$862.92		$932.1667	$932.17	$932.10	$932.20