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	$198.41	12.561%	$223.3323	$223.33	$223.35	$223.30
Purchase #2	$159.60	9.722%	$175.1163	$175.12	$175.10	$175.10
Purchase #3	$246.27	3.796%	$255.6184	$255.62	$255.60	$255.60
Purchase #4	$248.40	10.495%	$274.4696	$274.47	$274.45	$274.50
Purchase #5	$78.84	10.224%	$86.9006	$86.90	$86.90	$86.90
Purchase #6	$153.43	4.655%	$160.5722	$160.57	$160.55	$160.60
Purchase #7	$8.39	6.155%	$8.9064	$8.91	$8.90	$8.90
7 purchase totals =	$1,093.34		$1,184.9158	$1,184.92	$1,184.85	$1,184.90