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	$196.84	11.515%	$219.5061	$219.51	$219.50	$219.50
Purchase #2	$34.82	8.740%	$37.8633	$37.86	$37.85	$37.90
Purchase #3	$224.63	7.443%	$241.3492	$241.35	$241.35	$241.30
Purchase #4	$33.74	10.841%	$37.3978	$37.40	$37.40	$37.40
Purchase #5	$31.82	6.391%	$33.8536	$33.85	$33.85	$33.90
Purchase #6	$127.45	6.590%	$135.849	$135.85	$135.85	$135.80
Purchase #7	$127.38	4.267%	$132.8153	$132.82	$132.80	$132.80
7 purchase totals =	$776.68		$838.6343	$838.64	$838.60	$838.60