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	$55.46	12.684%	$62.4945	$62.49	$62.50	$62.50
Purchase #2	$207.48	3.803%	$215.3705	$215.37	$215.35	$215.40
Purchase #3	$54.47	8.634%	$59.1729	$59.17	$59.15	$59.20
Purchase #4	$195.61	4.696%	$204.7958	$204.80	$204.80	$204.80
Purchase #5	$147.53	8.180%	$159.598	$159.60	$159.60	$159.60
Purchase #6	$163.41	10.360%	$180.3393	$180.34	$180.35	$180.30
Purchase #7	$89.48	12.739%	$100.8789	$100.88	$100.90	$100.90
7 purchase totals =	$913.44		$982.6499	$982.65	$982.65	$982.70