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	$222.54	3.117%	$229.4766	$229.48	$229.50	$229.50
Purchase #2	$203.49	11.616%	$227.1274	$227.13	$227.15	$227.10
Purchase #3	$26.99	12.294%	$30.3082	$30.31	$30.30	$30.30
Purchase #4	$81.41	11.182%	$90.5133	$90.51	$90.50	$90.50
Purchase #5	$134.34	5.408%	$141.6051	$141.61	$141.60	$141.60
Purchase #6	$176.46	10.345%	$194.7148	$194.71	$194.70	$194.70
Purchase #7	$48.55	10.838%	$53.8118	$53.81	$53.80	$53.80
7 purchase totals =	$893.78		$967.5572	$967.56	$967.55	$967.50