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	$232.33	9.499%	$254.399	$254.40	$254.40	$254.40
Purchase #2	$117.85	5.185%	$123.9605	$123.96	$123.95	$124.00
Purchase #3	$173.58	13.296%	$196.6592	$196.66	$196.65	$196.70
Purchase #4	$233.47	9.614%	$255.9158	$255.92	$255.90	$255.90
Purchase #5	$92.36	5.558%	$97.4934	$97.49	$97.50	$97.50
Purchase #6	$9.38	13.433%	$10.64	$10.64	$10.65	$10.60
Purchase #7	$176.26	8.578%	$191.3796	$191.38	$191.40	$191.40
7 purchase totals =	$1,035.23		$1,130.4475	$1,130.45	$1,130.45	$1,130.50