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	$121.37	8.455%	$131.6318	$131.63	$131.65	$131.60
Purchase #2	$135.86	9.196%	$148.3537	$148.35	$148.35	$148.40
Purchase #3	$56.65	4.227%	$59.0446	$59.04	$59.05	$59.00
Purchase #4	$238.41	11.623%	$266.1204	$266.12	$266.10	$266.10
Purchase #5	$224.61	11.784%	$251.078	$251.08	$251.10	$251.10
Purchase #6	$100.84	4.718%	$105.5976	$105.60	$105.60	$105.60
Purchase #7	$200.80	9.239%	$219.3519	$219.35	$219.35	$219.40
7 purchase totals =	$1,078.54		$1,181.1780	$1,181.17	$1,181.20	$1,181.20