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	$134.87	7.232%	$144.6238	$144.62	$144.60	$144.60
Purchase #2	$7.39	3.469%	$7.6464	$7.65	$7.65	$7.60
Purchase #3	$152.33	9.180%	$166.3139	$166.31	$166.30	$166.30
Purchase #4	$89.46	12.333%	$100.4931	$100.49	$100.50	$100.50
Purchase #5	$143.49	13.257%	$162.5125	$162.51	$162.50	$162.50
Purchase #6	$136.86	3.118%	$141.1273	$141.13	$141.15	$141.10
Purchase #7	$61.41	4.606%	$64.2385	$64.24	$64.25	$64.20
7 purchase totals =	$725.81		$786.9555	$786.95	$786.95	$786.80