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	$210.34	7.277%	$225.6464	$225.65	$225.65	$225.60
Purchase #2	$28.61	9.269%	$31.2619	$31.26	$31.25	$31.30
Purchase #3	$99.96	3.736%	$103.6945	$103.69	$103.70	$103.70
Purchase #4	$74.56	5.405%	$78.59	$78.59	$78.60	$78.60
Purchase #5	$203.56	5.356%	$214.4627	$214.46	$214.45	$214.50
Purchase #6	$10.45	10.117%	$11.5072	$11.51	$11.50	$11.50
Purchase #7	$129.67	4.743%	$135.8202	$135.82	$135.80	$135.80
7 purchase totals =	$757.15		$800.9829	$800.98	$800.95	$801.00