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	$55.66	11.178%	$61.8817	$61.88	$61.90	$61.90
Purchase #2	$79.78	9.151%	$87.0807	$87.08	$87.10	$87.10
Purchase #3	$233.74	7.147%	$250.4454	$250.45	$250.45	$250.40
Purchase #4	$98.25	5.745%	$103.8945	$103.89	$103.90	$103.90
Purchase #5	$38.50	12.181%	$43.1897	$43.19	$43.20	$43.20
Purchase #6	$134.58	5.566%	$142.0707	$142.07	$142.05	$142.10
Purchase #7	$242.98	11.146%	$270.0626	$270.06	$270.05	$270.10
7 purchase totals =	$883.49		$958.6253	$958.62	$958.65	$958.70