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	$207.68	10.718%	$229.9391	$229.94	$229.95	$229.90
Purchase #2	$96.26	4.169%	$100.2731	$100.27	$100.25	$100.30
Purchase #3	$105.66	12.459%	$118.8242	$118.82	$118.80	$118.80
Purchase #4	$56.82	10.244%	$62.6406	$62.64	$62.65	$62.60
Purchase #5	$164.77	3.731%	$170.9176	$170.92	$170.90	$170.90
Purchase #6	$232.86	3.457%	$240.91	$240.91	$240.90	$240.90
Purchase #7	$28.27	11.776%	$31.5991	$31.60	$31.60	$31.60
7 purchase totals =	$892.32		$955.1037	$955.10	$955.05	$955.00