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	$209.83	5.730%	$221.8533	$221.85	$221.85	$221.90
Purchase #2	$14.89	3.339%	$15.3872	$15.39	$15.40	$15.40
Purchase #3	$71.65	9.550%	$78.4926	$78.49	$78.50	$78.50
Purchase #4	$54.65	10.447%	$60.3593	$60.36	$60.35	$60.40
Purchase #5	$183.73	11.119%	$204.1589	$204.16	$204.15	$204.20
Purchase #6	$249.83	11.218%	$277.8559	$277.86	$277.85	$277.90
Purchase #7	$216.85	5.320%	$228.3864	$228.39	$228.40	$228.40
7 purchase totals =	$1,001.43		$1,086.4936	$1,086.50	$1,086.50	$1,086.70