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	$181.54	6.609%	$193.538	$193.54	$193.55	$193.50
Purchase #2	$183.66	4.795%	$192.4665	$192.47	$192.45	$192.50
Purchase #3	$23.50	4.341%	$24.5201	$24.52	$24.50	$24.50
Purchase #4	$24.29	4.150%	$25.298	$25.30	$25.30	$25.30
Purchase #5	$241.59	12.386%	$271.5133	$271.51	$271.50	$271.50
Purchase #6	$85.50	13.287%	$96.8604	$96.86	$96.85	$96.90
Purchase #7	$56.61	8.377%	$61.3522	$61.35	$61.35	$61.40
7 purchase totals =	$796.69		$865.5485	$865.55	$865.50	$865.60