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	$42.82	11.778%	$47.8633	$47.86	$47.85	$47.90
Purchase #2	$134.71	12.394%	$151.406	$151.41	$151.40	$151.40
Purchase #3	$177.80	12.265%	$199.6072	$199.61	$199.60	$199.60
Purchase #4	$53.44	3.309%	$55.2083	$55.21	$55.20	$55.20
Purchase #5	$71.78	11.762%	$80.2228	$80.22	$80.20	$80.20
Purchase #6	$185.51	11.668%	$207.1553	$207.16	$207.15	$207.20
Purchase #7	$77.61	10.279%	$85.5875	$85.59	$85.60	$85.60
7 purchase totals =	$743.67		$827.0504	$827.06	$827.00	$827.10