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	$91.65	5.342%	$96.5459	$96.55	$96.55	$96.50
Purchase #2	$175.44	9.643%	$192.3577	$192.36	$192.35	$192.40
Purchase #3	$35.40	8.814%	$38.5202	$38.52	$38.50	$38.50
Purchase #4	$119.69	6.762%	$127.7834	$127.78	$127.80	$127.80
Purchase #5	$109.60	12.247%	$123.0227	$123.02	$123.00	$123.00
Purchase #6	$124.73	13.574%	$141.6609	$141.66	$141.65	$141.70
Purchase #7	$10.45	5.466%	$11.0212	$11.02	$11.00	$11.00
7 purchase totals =	$666.96		$730.9120	$730.91	$730.85	$730.90