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	$155.94	8.268%	$168.8331	$168.83	$168.85	$168.80
Purchase #2	$164.55	3.468%	$170.2566	$170.26	$170.25	$170.30
Purchase #3	$174.82	12.177%	$196.1078	$196.11	$196.10	$196.10
Purchase #4	$221.26	12.218%	$248.2935	$248.29	$248.30	$248.30
Purchase #5	$143.37	6.368%	$152.4998	$152.50	$152.50	$152.50
Purchase #6	$72.30	10.687%	$80.0267	$80.03	$80.05	$80.00
Purchase #7	$123.76	6.763%	$132.1299	$132.13	$132.15	$132.10
7 purchase totals =	$1,056.00		$1,148.1474	$1,148.15	$1,148.20	$1,148.10