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	$184.93	6.471%	$196.8968	$196.90	$196.90	$196.90
Purchase #2	$82.67	8.677%	$89.8433	$89.84	$89.85	$89.80
Purchase #3	$115.89	8.152%	$125.3374	$125.34	$125.35	$125.30
Purchase #4	$145.57	7.385%	$156.3203	$156.32	$156.30	$156.30
Purchase #5	$5.47	11.493%	$6.0987	$6.10	$6.10	$6.10
Purchase #6	$134.28	6.676%	$143.2445	$143.24	$143.25	$143.20
Purchase #7	$204.73	11.674%	$228.6302	$228.63	$228.65	$228.60
7 purchase totals =	$873.54		$946.3712	$946.37	$946.40	$946.20