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	$187.78	7.391%	$201.6588	$201.66	$201.65	$201.70
Purchase #2	$53.38	5.567%	$56.3517	$56.35	$56.35	$56.40
Purchase #3	$68.81	6.788%	$73.4808	$73.48	$73.50	$73.50
Purchase #4	$243.88	6.143%	$258.8615	$258.86	$258.85	$258.90
Purchase #5	$169.89	11.725%	$189.8096	$189.81	$189.80	$189.80
Purchase #6	$196.43	12.456%	$220.8973	$220.90	$220.90	$220.90
Purchase #7	$83.28	7.609%	$89.6168	$89.62	$89.60	$89.60
7 purchase totals =	$1,003.45		$1,090.6765	$1,090.68	$1,090.65	$1,090.80