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	$54.94	8.232%	$59.4627	$59.46	$59.45	$59.50
Purchase #2	$120.35	9.604%	$131.9084	$131.91	$131.90	$131.90
Purchase #3	$190.44	3.798%	$197.6729	$197.67	$197.65	$197.70
Purchase #4	$149.81	6.723%	$159.8817	$159.88	$159.90	$159.90
Purchase #5	$118.55	3.784%	$123.0359	$123.04	$123.05	$123.00
Purchase #6	$58.28	10.461%	$64.3767	$64.38	$64.40	$64.40
Purchase #7	$194.99	13.858%	$222.0117	$222.01	$222.00	$222.00
7 purchase totals =	$887.36		$958.3500	$958.35	$958.35	$958.40