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	$203.57	5.386%	$214.5343	$214.53	$214.55	$214.50
Purchase #2	$212.92	12.360%	$239.2369	$239.24	$239.25	$239.20
Purchase #3	$205.53	6.676%	$219.2512	$219.25	$219.25	$219.30
Purchase #4	$245.30	13.114%	$277.4686	$277.47	$277.45	$277.50
Purchase #5	$80.66	12.721%	$90.9208	$90.92	$90.90	$90.90
Purchase #6	$135.92	9.131%	$148.3309	$148.33	$148.35	$148.30
Purchase #7	$138.91	3.285%	$143.4732	$143.47	$143.45	$143.50
7 purchase totals =	$1,222.81		$1,333.2159	$1,333.21	$1,333.20	$1,333.20