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	$185.56	5.549%	$195.8567	$195.86	$195.85	$195.90
Purchase #2	$37.41	10.828%	$41.4608	$41.46	$41.45	$41.50
Purchase #3	$52.40	6.447%	$55.7782	$55.78	$55.80	$55.80
Purchase #4	$74.30	12.724%	$83.7539	$83.75	$83.75	$83.80
Purchase #5	$61.65	7.593%	$66.3311	$66.33	$66.35	$66.30
Purchase #6	$183.81	4.280%	$191.6771	$191.68	$191.70	$191.70
Purchase #7	$75.65	8.758%	$82.2754	$82.28	$82.30	$82.30
7 purchase totals =	$670.78		$717.1332	$717.14	$717.20	$717.30