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	$133.29	4.421%	$139.1828	$139.18	$139.20	$139.20
Purchase #2	$10.89	6.395%	$11.5864	$11.59	$11.60	$11.60
Purchase #3	$78.49	11.539%	$87.547	$87.55	$87.55	$87.50
Purchase #4	$152.86	6.431%	$162.6904	$162.69	$162.70	$162.70
Purchase #5	$127.37	3.618%	$131.9782	$131.98	$132.00	$132.00
Purchase #6	$167.62	7.570%	$180.3088	$180.31	$180.30	$180.30
Purchase #7	$98.30	3.363%	$101.6058	$101.61	$101.60	$101.60
7 purchase totals =	$768.82		$814.8994	$814.91	$814.95	$814.90