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	$75.98	8.568%	$82.49	$82.49	$82.50	$82.50
Purchase #2	$150.27	6.404%	$159.8933	$159.89	$159.90	$159.90
Purchase #3	$214.60	5.117%	$225.5811	$225.58	$225.60	$225.60
Purchase #4	$194.37	11.766%	$217.2396	$217.24	$217.25	$217.20
Purchase #5	$105.48	9.491%	$115.4911	$115.49	$115.50	$115.50
Purchase #6	$248.72	3.114%	$256.4651	$256.47	$256.45	$256.50
Purchase #7	$67.98	8.591%	$73.8202	$73.82	$73.80	$73.80
7 purchase totals =	$1,057.40		$1,130.9804	$1,130.98	$1,131.00	$1,131.00