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	$68.51	4.512%	$71.6012	$71.60	$71.60	$71.60
Purchase #2	$39.78	9.365%	$43.5054	$43.51	$43.50	$43.50
Purchase #3	$138.98	5.325%	$146.3807	$146.38	$146.40	$146.40
Purchase #4	$63.80	10.204%	$70.3102	$70.31	$70.30	$70.30
Purchase #5	$223.65	5.314%	$235.5348	$235.53	$235.55	$235.50
Purchase #6	$210.39	3.344%	$217.4254	$217.43	$217.45	$217.40
Purchase #7	$39.75	3.159%	$41.0057	$41.01	$41.00	$41.00
7 purchase totals =	$784.86		$825.7634	$825.77	$825.80	$825.70