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	$191.33	10.255%	$210.9509	$210.95	$210.95	$211.00
Purchase #2	$149.34	12.859%	$168.5436	$168.54	$168.55	$168.50
Purchase #3	$56.44	5.125%	$59.3326	$59.33	$59.35	$59.30
Purchase #4	$185.81	3.318%	$191.9752	$191.98	$192.00	$192.00
Purchase #5	$113.73	5.730%	$120.2467	$120.25	$120.25	$120.20
Purchase #6	$145.28	6.166%	$154.238	$154.24	$154.25	$154.20
Purchase #7	$204.59	8.794%	$222.5816	$222.58	$222.60	$222.60
7 purchase totals =	$1,046.52		$1,127.8686	$1,127.87	$1,127.95	$1,127.80