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	$92.47	4.155%	$96.3121	$96.31	$96.30	$96.30
Purchase #2	$127.63	3.458%	$132.0434	$132.04	$132.05	$132.00
Purchase #3	$28.45	11.121%	$31.6139	$31.61	$31.60	$31.60
Purchase #4	$27.63	5.747%	$29.2179	$29.22	$29.20	$29.20
Purchase #5	$144.68	5.151%	$152.1325	$152.13	$152.15	$152.10
Purchase #6	$145.78	3.736%	$151.2263	$151.23	$151.25	$151.20
Purchase #7	$223.64	7.666%	$240.7842	$240.78	$240.80	$240.80
7 purchase totals =	$790.28		$833.3303	$833.32	$833.35	$833.20