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	$148.76	11.631%	$166.0623	$166.06	$166.05	$166.10
Purchase #2	$58.29	13.169%	$65.9662	$65.97	$65.95	$66.00
Purchase #3	$157.74	9.283%	$172.383	$172.38	$172.40	$172.40
Purchase #4	$180.83	8.321%	$195.8769	$195.88	$195.90	$195.90
Purchase #5	$94.40	6.742%	$100.7644	$100.76	$100.75	$100.80
Purchase #6	$242.53	6.843%	$259.1263	$259.13	$259.15	$259.10
Purchase #7	$69.31	12.661%	$78.0853	$78.09	$78.10	$78.10
7 purchase totals =	$951.86		$1,038.2644	$1,038.27	$1,038.30	$1,038.40