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	$143.65	8.274%	$155.5356	$155.54	$155.55	$155.50
Purchase #2	$162.27	5.682%	$171.4902	$171.49	$171.50	$171.50
Purchase #3	$33.74	4.844%	$35.3744	$35.37	$35.35	$35.40
Purchase #4	$105.27	13.534%	$119.5172	$119.52	$119.50	$119.50
Purchase #5	$239.79	7.850%	$258.6135	$258.61	$258.60	$258.60
Purchase #6	$133.30	3.713%	$138.2494	$138.25	$138.25	$138.20
Purchase #7	$249.55	6.777%	$266.462	$266.46	$266.45	$266.50
7 purchase totals =	$1,067.57		$1,145.2423	$1,145.24	$1,145.20	$1,145.20