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	$160.76	4.861%	$168.5745	$168.57	$168.55	$168.60
Purchase #2	$201.53	4.784%	$211.1712	$211.17	$211.15	$211.20
Purchase #3	$128.44	12.346%	$144.2972	$144.30	$144.30	$144.30
Purchase #4	$50.78	8.802%	$55.2497	$55.25	$55.25	$55.20
Purchase #5	$210.29	11.401%	$234.2652	$234.27	$234.25	$234.30
Purchase #6	$72.71	4.223%	$75.7805	$75.78	$75.80	$75.80
Purchase #7	$138.39	7.388%	$148.6143	$148.61	$148.60	$148.60
7 purchase totals =	$962.90		$1,037.9526	$1,037.95	$1,037.90	$1,038.00