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	$182.68	7.732%	$196.8048	$196.80	$196.80	$196.80
Purchase #2	$78.73	10.274%	$86.8187	$86.82	$86.80	$86.80
Purchase #3	$52.33	8.156%	$56.598	$56.60	$56.60	$56.60
Purchase #4	$10.84	4.367%	$11.3134	$11.31	$11.30	$11.30
Purchase #5	$114.57	11.614%	$127.8762	$127.88	$127.90	$127.90
Purchase #6	$170.82	12.822%	$192.7225	$192.72	$192.70	$192.70
Purchase #7	$15.92	4.120%	$16.5759	$16.58	$16.60	$16.60
7 purchase totals =	$625.89		$688.7095	$688.71	$688.70	$688.70