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	$184.77	6.229%	$196.2793	$196.28	$196.30	$196.30
Purchase #2	$71.31	7.651%	$76.7659	$76.77	$76.75	$76.80
Purchase #3	$122.78	13.741%	$139.6512	$139.65	$139.65	$139.70
Purchase #4	$90.36	11.191%	$100.4722	$100.47	$100.45	$100.50
Purchase #5	$94.58	10.759%	$104.7559	$104.76	$104.75	$104.80
Purchase #6	$207.45	7.744%	$223.5149	$223.51	$223.50	$223.50
Purchase #7	$156.48	9.652%	$171.5834	$171.58	$171.60	$171.60
7 purchase totals =	$927.73		$1,013.0228	$1,013.02	$1,013.00	$1,013.20