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	$228.26	4.393%	$238.2875	$238.29	$238.30	$238.30
Purchase #2	$55.80	6.235%	$59.2791	$59.28	$59.30	$59.30
Purchase #3	$30.87	4.853%	$32.3681	$32.37	$32.35	$32.40
Purchase #4	$42.46	11.365%	$47.2856	$47.29	$47.30	$47.30
Purchase #5	$220.58	10.502%	$243.7453	$243.75	$243.75	$243.70
Purchase #6	$74.97	5.121%	$78.8092	$78.81	$78.80	$78.80
Purchase #7	$80.53	7.668%	$86.705	$86.71	$86.70	$86.70
7 purchase totals =	$733.47		$786.4798	$786.50	$786.50	$786.50