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	$134.33	12.569%	$151.2139	$151.21	$151.20	$151.20
Purchase #2	$23.84	6.148%	$25.3057	$25.31	$25.30	$25.30
Purchase #3	$168.29	9.698%	$184.6108	$184.61	$184.60	$184.60
Purchase #4	$164.29	5.699%	$173.6529	$173.65	$173.65	$173.70
Purchase #5	$141.48	5.236%	$148.8879	$148.89	$148.90	$148.90
Purchase #6	$104.35	5.280%	$109.8597	$109.86	$109.85	$109.90
Purchase #7	$96.73	12.155%	$108.4875	$108.49	$108.50	$108.50
7 purchase totals =	$833.31		$902.0184	$902.02	$902.00	$902.10