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	$195.73	12.810%	$220.803	$220.80	$220.80	$220.80
Purchase #2	$150.94	12.406%	$169.6656	$169.67	$169.65	$169.70
Purchase #3	$196.32	11.456%	$218.8104	$218.81	$218.80	$218.80
Purchase #4	$34.47	12.846%	$38.898	$38.90	$38.90	$38.90
Purchase #5	$39.74	6.355%	$42.2655	$42.27	$42.25	$42.30
Purchase #6	$140.46	11.140%	$156.1072	$156.11	$156.10	$156.10
Purchase #7	$215.46	7.437%	$231.4838	$231.48	$231.50	$231.50
7 purchase totals =	$973.12		$1,078.0335	$1,078.04	$1,078.00	$1,078.10