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	$94.85	11.711%	$105.9579	$105.96	$105.95	$106.00
Purchase #2	$167.25	7.516%	$179.8205	$179.82	$179.80	$179.80
Purchase #3	$197.67	12.691%	$222.7563	$222.76	$222.75	$222.80
Purchase #4	$91.27	6.121%	$96.8566	$96.86	$96.85	$96.90
Purchase #5	$247.71	3.513%	$256.4121	$256.41	$256.40	$256.40
Purchase #6	$8.43	12.763%	$9.5059	$9.51	$9.50	$9.50
Purchase #7	$100.66	8.872%	$109.5906	$109.59	$109.60	$109.60
7 purchase totals =	$907.84		$980.8999	$980.91	$980.85	$981.00