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	$248.58	9.631%	$272.5207	$272.52	$272.50	$272.50
Purchase #2	$90.27	4.566%	$94.3917	$94.39	$94.40	$94.40
Purchase #3	$84.50	5.114%	$88.8213	$88.82	$88.80	$88.80
Purchase #4	$248.41	3.394%	$256.841	$256.84	$256.85	$256.80
Purchase #5	$63.74	12.767%	$71.8777	$71.88	$71.90	$71.90
Purchase #6	$91.37	8.441%	$99.0825	$99.08	$99.10	$99.10
Purchase #7	$157.87	8.545%	$171.36	$171.36	$171.35	$171.40
7 purchase totals =	$984.74		$1,054.8949	$1,054.89	$1,054.90	$1,054.90