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	$79.38	13.727%	$90.2765	$90.28	$90.30	$90.30
Purchase #2	$197.98	13.631%	$224.9667	$224.97	$224.95	$225.00
Purchase #3	$74.56	11.330%	$83.0076	$83.01	$83.00	$83.00
Purchase #4	$242.35	3.503%	$250.8395	$250.84	$250.85	$250.80
Purchase #5	$119.82	5.297%	$126.1669	$126.17	$126.15	$126.20
Purchase #6	$130.30	12.402%	$146.4598	$146.46	$146.45	$146.50
Purchase #7	$117.40	12.824%	$132.4554	$132.46	$132.45	$132.50
7 purchase totals =	$961.79		$1,054.1724	$1,054.19	$1,054.15	$1,054.30