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	$148.52	5.799%	$157.1327	$157.13	$157.15	$157.10
Purchase #2	$150.92	11.837%	$168.7844	$168.78	$168.80	$168.80
Purchase #3	$210.90	3.140%	$217.5223	$217.52	$217.50	$217.50
Purchase #4	$87.62	13.285%	$99.2603	$99.26	$99.25	$99.30
Purchase #5	$136.36	10.125%	$150.1665	$150.17	$150.15	$150.20
Purchase #6	$62.82	3.867%	$65.2492	$65.25	$65.25	$65.20
Purchase #7	$195.27	7.703%	$210.3116	$210.31	$210.30	$210.30
7 purchase totals =	$992.41		$1,068.4270	$1,068.42	$1,068.40	$1,068.40