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	$152.58	10.239%	$168.2027	$168.20	$168.20	$168.20
Purchase #2	$111.33	10.862%	$123.4227	$123.42	$123.40	$123.40
Purchase #3	$77.40	8.394%	$83.897	$83.90	$83.90	$83.90
Purchase #4	$12.79	5.173%	$13.4516	$13.45	$13.45	$13.50
Purchase #5	$152.40	5.847%	$161.3108	$161.31	$161.30	$161.30
Purchase #6	$68.40	3.417%	$70.7372	$70.74	$70.75	$70.70
Purchase #7	$102.96	8.221%	$111.4243	$111.42	$111.40	$111.40
7 purchase totals =	$677.86		$732.4463	$732.44	$732.40	$732.40