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	$114.31	7.723%	$123.1382	$123.14	$123.15	$123.10
Purchase #2	$172.45	7.136%	$184.756	$184.76	$184.75	$184.80
Purchase #3	$97.95	12.162%	$109.8627	$109.86	$109.85	$109.90
Purchase #4	$128.29	10.334%	$141.5475	$141.55	$141.55	$141.50
Purchase #5	$249.74	8.611%	$271.2451	$271.25	$271.25	$271.20
Purchase #6	$65.37	9.603%	$71.6475	$71.65	$71.65	$71.60
Purchase #7	$235.25	4.816%	$246.5796	$246.58	$246.60	$246.60
7 purchase totals =	$1,063.36		$1,148.7766	$1,148.79	$1,148.80	$1,148.70