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	$184.54	6.742%	$196.9817	$196.98	$197.00	$197.00
Purchase #2	$32.96	12.736%	$37.1578	$37.16	$37.15	$37.20
Purchase #3	$18.71	9.335%	$20.4566	$20.46	$20.45	$20.50
Purchase #4	$112.40	6.631%	$119.8532	$119.85	$119.85	$119.90
Purchase #5	$113.42	12.156%	$127.2073	$127.21	$127.20	$127.20
Purchase #6	$60.35	4.218%	$62.8956	$62.90	$62.90	$62.90
Purchase #7	$245.28	9.808%	$269.3371	$269.34	$269.35	$269.30
7 purchase totals =	$767.66		$833.8893	$833.90	$833.90	$834.00