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	$189.67	11.254%	$211.0155	$211.02	$211.00	$211.00
Purchase #2	$132.97	3.153%	$137.1625	$137.16	$137.15	$137.20
Purchase #3	$102.79	6.570%	$109.5433	$109.54	$109.55	$109.50
Purchase #4	$63.39	12.570%	$71.3581	$71.36	$71.35	$71.40
Purchase #5	$228.67	7.196%	$245.1251	$245.13	$245.15	$245.10
Purchase #6	$148.53	5.490%	$156.6843	$156.68	$156.70	$156.70
Purchase #7	$141.30	10.194%	$155.7041	$155.70	$155.70	$155.70
7 purchase totals =	$1,007.32		$1,086.5929	$1,086.59	$1,086.60	$1,086.60