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	$82.88	4.143%	$86.3137	$86.31	$86.30	$86.30
Purchase #2	$183.47	3.709%	$190.2749	$190.27	$190.25	$190.30
Purchase #3	$10.67	7.156%	$11.4335	$11.43	$11.45	$11.40
Purchase #4	$224.64	5.258%	$236.4516	$236.45	$236.45	$236.50
Purchase #5	$42.28	9.460%	$46.2797	$46.28	$46.30	$46.30
Purchase #6	$242.54	10.500%	$268.0067	$268.01	$268.00	$268.00
Purchase #7	$17.82	9.516%	$19.5158	$19.52	$19.50	$19.50
7 purchase totals =	$804.30		$858.2759	$858.27	$858.25	$858.30