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	$170.48	6.800%	$182.0726	$182.07	$182.05	$182.10
Purchase #2	$194.89	5.327%	$205.2718	$205.27	$205.25	$205.30
Purchase #3	$179.55	5.485%	$189.3983	$189.40	$189.40	$189.40
Purchase #4	$57.47	3.565%	$59.5188	$59.52	$59.50	$59.50
Purchase #5	$69.37	11.844%	$77.5862	$77.59	$77.60	$77.60
Purchase #6	$215.95	12.643%	$243.2526	$243.25	$243.25	$243.30
Purchase #7	$18.67	11.750%	$20.8637	$20.86	$20.85	$20.90
7 purchase totals =	$906.38		$977.9640	$977.96	$977.90	$978.10