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	$19.82	5.271%	$20.8647	$20.86	$20.85	$20.90
Purchase #2	$174.78	3.411%	$180.7417	$180.74	$180.75	$180.70
Purchase #3	$81.79	3.789%	$84.889	$84.89	$84.90	$84.90
Purchase #4	$88.91	12.823%	$100.3109	$100.31	$100.30	$100.30
Purchase #5	$208.66	11.787%	$233.2548	$233.25	$233.25	$233.30
Purchase #6	$191.31	12.707%	$215.6198	$215.62	$215.60	$215.60
Purchase #7	$37.80	10.248%	$41.6737	$41.67	$41.65	$41.70
7 purchase totals =	$803.07		$877.3546	$877.34	$877.30	$877.40