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	$87.42	10.136%	$96.2809	$96.28	$96.30	$96.30
Purchase #2	$141.57	13.797%	$161.1024	$161.10	$161.10	$161.10
Purchase #3	$229.62	7.406%	$246.6257	$246.63	$246.65	$246.60
Purchase #4	$103.80	7.460%	$111.5435	$111.54	$111.55	$111.50
Purchase #5	$77.86	6.738%	$83.1062	$83.11	$83.10	$83.10
Purchase #6	$74.59	7.596%	$80.2559	$80.26	$80.25	$80.30
Purchase #7	$213.99	5.149%	$225.0083	$225.01	$225.00	$225.00
7 purchase totals =	$928.85		$1,003.9229	$1,003.93	$1,003.95	$1,003.90