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	$138.82	8.248%	$150.2699	$150.27	$150.25	$150.30
Purchase #2	$33.33	12.502%	$37.4969	$37.50	$37.50	$37.50
Purchase #3	$77.90	5.578%	$82.2453	$82.25	$82.25	$82.20
Purchase #4	$237.71	5.363%	$250.4584	$250.46	$250.45	$250.50
Purchase #5	$206.92	12.802%	$233.4099	$233.41	$233.40	$233.40
Purchase #6	$72.92	3.528%	$75.4926	$75.49	$75.50	$75.50
Purchase #7	$114.93	10.743%	$127.2769	$127.28	$127.30	$127.30
7 purchase totals =	$882.53		$956.6499	$956.66	$956.65	$956.70