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	$146.88	6.435%	$156.3317	$156.33	$156.35	$156.30
Purchase #2	$245.46	8.709%	$266.8371	$266.84	$266.85	$266.80
Purchase #3	$100.39	11.563%	$111.9981	$112.00	$112.00	$112.00
Purchase #4	$196.30	6.443%	$208.9476	$208.95	$208.95	$208.90
Purchase #5	$85.54	13.168%	$96.8039	$96.80	$96.80	$96.80
Purchase #6	$235.65	8.841%	$256.4838	$256.48	$256.50	$256.50
Purchase #7	$13.51	13.680%	$15.3582	$15.36	$15.35	$15.40
7 purchase totals =	$1,023.73		$1,112.7604	$1,112.76	$1,112.80	$1,112.70