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	$239.75	5.796%	$253.6459	$253.65	$253.65	$253.60
Purchase #2	$245.27	13.780%	$279.0682	$279.07	$279.05	$279.10
Purchase #3	$55.27	10.798%	$61.2381	$61.24	$61.25	$61.20
Purchase #4	$232.26	6.301%	$246.8947	$246.89	$246.90	$246.90
Purchase #5	$110.28	7.780%	$118.8598	$118.86	$118.85	$118.90
Purchase #6	$66.72	6.863%	$71.299	$71.30	$71.30	$71.30
Purchase #7	$64.95	3.605%	$67.2914	$67.29	$67.30	$67.30
7 purchase totals =	$1,014.50		$1,098.2971	$1,098.30	$1,098.30	$1,098.30