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	$28.26	8.868%	$30.7661	$30.77	$30.75	$30.80
Purchase #2	$38.43	13.678%	$43.6865	$43.69	$43.70	$43.70
Purchase #3	$32.42	12.255%	$36.3931	$36.39	$36.40	$36.40
Purchase #4	$189.30	8.822%	$206	$206.00	$206.00	$206.00
Purchase #5	$117.98	8.338%	$127.8172	$127.82	$127.80	$127.80
Purchase #6	$52.62	13.439%	$59.6916	$59.69	$59.70	$59.70
Purchase #7	$79.36	13.748%	$90.2704	$90.27	$90.25	$90.30
7 purchase totals =	$538.37		$594.6249	$594.63	$594.60	$594.70