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	$65.91	8.427%	$71.4642	$71.46	$71.45	$71.50
Purchase #2	$50.57	5.161%	$53.1799	$53.18	$53.20	$53.20
Purchase #3	$67.32	7.340%	$72.2613	$72.26	$72.25	$72.30
Purchase #4	$197.57	6.211%	$209.8411	$209.84	$209.85	$209.80
Purchase #5	$234.76	8.556%	$254.8461	$254.85	$254.85	$254.80
Purchase #6	$36.71	10.389%	$40.5238	$40.52	$40.50	$40.50
Purchase #7	$233.57	6.293%	$248.2686	$248.27	$248.25	$248.30
7 purchase totals =	$886.41		$950.3850	$950.38	$950.35	$950.40