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	$103.59	4.823%	$108.5861	$108.59	$108.60	$108.60
Purchase #2	$144.72	4.727%	$151.5609	$151.56	$151.55	$151.60
Purchase #3	$78.33	5.847%	$82.91	$82.91	$82.90	$82.90
Purchase #4	$99.50	5.693%	$105.1645	$105.16	$105.15	$105.20
Purchase #5	$71.57	9.536%	$78.3949	$78.39	$78.40	$78.40
Purchase #6	$71.37	6.119%	$75.7371	$75.74	$75.75	$75.70
Purchase #7	$209.50	4.297%	$218.5022	$218.50	$218.50	$218.50
7 purchase totals =	$778.58		$820.8557	$820.85	$820.85	$820.90