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	$61.55	4.347%	$64.2256	$64.23	$64.25	$64.20
Purchase #2	$87.54	3.856%	$90.9155	$90.92	$90.90	$90.90
Purchase #3	$117.87	8.126%	$127.4481	$127.45	$127.45	$127.40
Purchase #4	$109.86	11.332%	$122.3093	$122.31	$122.30	$122.30
Purchase #5	$58.98	10.589%	$65.2254	$65.23	$65.25	$65.20
Purchase #6	$189.34	3.216%	$195.4292	$195.43	$195.45	$195.40
Purchase #7	$245.56	11.549%	$273.9197	$273.92	$273.90	$273.90
7 purchase totals =	$870.70		$939.4728	$939.49	$939.50	$939.30