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	$54.79	8.873%	$59.6515	$59.65	$59.65	$59.70
Purchase #2	$75.77	6.606%	$80.7754	$80.78	$80.80	$80.80
Purchase #3	$137.49	3.382%	$142.1399	$142.14	$142.15	$142.10
Purchase #4	$209.76	11.871%	$234.6606	$234.66	$234.65	$234.70
Purchase #5	$132.75	6.784%	$141.7558	$141.76	$141.75	$141.80
Purchase #6	$211.32	9.570%	$231.5433	$231.54	$231.55	$231.50
Purchase #7	$163.72	4.336%	$170.8189	$170.82	$170.80	$170.80
7 purchase totals =	$985.60		$1,061.3454	$1,061.35	$1,061.35	$1,061.40