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	$245.27	5.564%	$258.9168	$258.92	$258.90	$258.90
Purchase #2	$152.79	10.416%	$168.7046	$168.70	$168.70	$168.70
Purchase #3	$143.80	5.306%	$151.43	$151.43	$151.45	$151.40
Purchase #4	$43.56	4.330%	$45.4461	$45.45	$45.45	$45.40
Purchase #5	$204.27	6.300%	$217.139	$217.14	$217.15	$217.10
Purchase #6	$190.74	9.638%	$209.1235	$209.12	$209.10	$209.10
Purchase #7	$178.28	6.826%	$190.4494	$190.45	$190.45	$190.40
7 purchase totals =	$1,158.71		$1,241.2094	$1,241.21	$1,241.20	$1,241.00