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	$235.63	12.583%	$265.2793	$265.28	$265.30	$265.30
Purchase #2	$90.48	7.252%	$97.0416	$97.04	$97.05	$97.00
Purchase #3	$217.71	11.677%	$243.132	$243.13	$243.15	$243.10
Purchase #4	$12.31	13.405%	$13.9602	$13.96	$13.95	$14.00
Purchase #5	$150.35	8.268%	$162.7809	$162.78	$162.80	$162.80
Purchase #6	$207.70	6.462%	$221.1216	$221.12	$221.10	$221.10
Purchase #7	$145.94	4.509%	$152.5204	$152.52	$152.50	$152.50
7 purchase totals =	$1,060.12		$1,155.8360	$1,155.83	$1,155.85	$1,155.80