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	$97.86	5.265%	$103.0123	$103.01	$103.00	$103.00
Purchase #2	$59.28	13.299%	$67.1636	$67.16	$67.15	$67.20
Purchase #3	$152.85	13.568%	$173.5887	$173.59	$173.60	$173.60
Purchase #4	$112.76	7.444%	$121.1539	$121.15	$121.15	$121.20
Purchase #5	$63.66	11.555%	$71.0159	$71.02	$71.00	$71.00
Purchase #6	$183.27	13.687%	$208.3542	$208.35	$208.35	$208.40
Purchase #7	$160.75	12.665%	$181.109	$181.11	$181.10	$181.10
7 purchase totals =	$830.43		$925.3976	$925.39	$925.35	$925.50