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	$212.28	8.678%	$230.7017	$230.70	$230.70	$230.70
Purchase #2	$71.71	12.407%	$80.6071	$80.61	$80.60	$80.60
Purchase #3	$93.36	13.300%	$105.7769	$105.78	$105.80	$105.80
Purchase #4	$237.29	4.118%	$247.0616	$247.06	$247.05	$247.10
Purchase #5	$139.33	12.284%	$156.4453	$156.45	$156.45	$156.40
Purchase #6	$34.52	4.284%	$35.9988	$36.00	$36.00	$36.00
Purchase #7	$151.33	7.270%	$162.3317	$162.33	$162.35	$162.30
7 purchase totals =	$939.82		$1,018.9231	$1,018.93	$1,018.95	$1,018.90