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	$181.31	10.766%	$200.8298	$200.83	$200.85	$200.80
Purchase #2	$116.51	8.571%	$126.4961	$126.50	$126.50	$126.50
Purchase #3	$171.96	9.545%	$188.3736	$188.37	$188.35	$188.40
Purchase #4	$239.32	10.144%	$263.5966	$263.60	$263.60	$263.60
Purchase #5	$30.47	6.220%	$32.3652	$32.37	$32.35	$32.40
Purchase #6	$68.76	12.513%	$77.3639	$77.36	$77.35	$77.40
Purchase #7	$215.29	5.575%	$227.2924	$227.29	$227.30	$227.30
7 purchase totals =	$1,023.62		$1,116.3176	$1,116.32	$1,116.30	$1,116.40