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	$186.75	5.228%	$196.5133	$196.51	$196.50	$196.50
Purchase #2	$147.38	12.423%	$165.689	$165.69	$165.70	$165.70
Purchase #3	$184.50	8.660%	$200.4777	$200.48	$200.50	$200.50
Purchase #4	$40.28	6.396%	$42.8563	$42.86	$42.85	$42.90
Purchase #5	$85.29	12.571%	$96.0118	$96.01	$96.00	$96.00
Purchase #6	$95.82	9.811%	$105.2209	$105.22	$105.20	$105.20
Purchase #7	$141.33	6.841%	$150.9984	$151.00	$151.00	$151.00
7 purchase totals =	$881.35		$957.7674	$957.77	$957.75	$957.80