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	$91.36	13.412%	$103.6132	$103.61	$103.60	$103.60
Purchase #2	$192.84	11.571%	$215.1535	$215.15	$215.15	$215.20
Purchase #3	$53.33	7.452%	$57.3042	$57.30	$57.30	$57.30
Purchase #4	$198.51	8.777%	$215.9332	$215.93	$215.95	$215.90
Purchase #5	$141.97	6.188%	$150.7551	$150.76	$150.75	$150.80
Purchase #6	$206.78	11.788%	$231.1552	$231.16	$231.15	$231.20
Purchase #7	$172.53	3.159%	$177.9802	$177.98	$178.00	$178.00
7 purchase totals =	$1,057.32		$1,151.8946	$1,151.89	$1,151.90	$1,152.00