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	$244.40	7.498%	$262.7251	$262.73	$262.75	$262.70
Purchase #2	$228.43	11.365%	$254.3911	$254.39	$254.40	$254.40
Purchase #3	$29.56	11.293%	$32.8982	$32.90	$32.90	$32.90
Purchase #4	$104.79	13.814%	$119.2657	$119.27	$119.25	$119.30
Purchase #5	$188.99	7.855%	$203.8352	$203.84	$203.85	$203.80
Purchase #6	$153.38	8.560%	$166.5093	$166.51	$166.50	$166.50
Purchase #7	$144.41	11.437%	$160.9262	$160.93	$160.95	$160.90
7 purchase totals =	$1,093.96		$1,200.5508	$1,200.57	$1,200.60	$1,200.50