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	$58.31	12.832%	$65.7923	$65.79	$65.80	$65.80
Purchase #2	$213.56	8.735%	$232.2145	$232.21	$232.20	$232.20
Purchase #3	$83.39	7.168%	$89.3674	$89.37	$89.35	$89.40
Purchase #4	$16.70	8.780%	$18.1663	$18.17	$18.15	$18.20
Purchase #5	$29.67	5.757%	$31.3781	$31.38	$31.40	$31.40
Purchase #6	$161.37	6.728%	$172.227	$172.23	$172.25	$172.20
Purchase #7	$101.42	3.761%	$105.2344	$105.23	$105.25	$105.20
7 purchase totals =	$664.42		$714.3800	$714.38	$714.40	$714.40