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	$112.27	11.846%	$125.5695	$125.57	$125.55	$125.60
Purchase #2	$44.90	11.708%	$50.1569	$50.16	$50.15	$50.20
Purchase #3	$87.54	13.696%	$99.5295	$99.53	$99.55	$99.50
Purchase #4	$94.63	5.649%	$99.9756	$99.98	$100.00	$100.00
Purchase #5	$89.41	10.153%	$98.4878	$98.49	$98.50	$98.50
Purchase #6	$29.40	4.182%	$30.6295	$30.63	$30.65	$30.60
Purchase #7	$30.65	10.278%	$33.8002	$33.80	$33.80	$33.80
7 purchase totals =	$488.80		$538.1490	$538.16	$538.20	$538.20