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	$47.63	10.684%	$52.7188	$52.72	$52.70	$52.70
Purchase #2	$209.85	6.705%	$223.9204	$223.92	$223.90	$223.90
Purchase #3	$241.65	3.743%	$250.695	$250.70	$250.70	$250.70
Purchase #4	$53.35	11.755%	$59.6213	$59.62	$59.60	$59.60
Purchase #5	$125.76	13.586%	$142.8458	$142.85	$142.85	$142.80
Purchase #6	$123.27	7.564%	$132.5941	$132.59	$132.60	$132.60
Purchase #7	$134.56	12.568%	$151.4715	$151.47	$151.45	$151.50
7 purchase totals =	$936.07		$1,013.8669	$1,013.87	$1,013.80	$1,013.80