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	$85.41	12.294%	$95.9103	$95.91	$95.90	$95.90
Purchase #2	$75.89	8.676%	$82.4742	$82.47	$82.45	$82.50
Purchase #3	$77.76	12.543%	$87.5134	$87.51	$87.50	$87.50
Purchase #4	$67.30	4.555%	$70.3655	$70.37	$70.35	$70.40
Purchase #5	$185.39	5.727%	$196.0073	$196.01	$196.00	$196.00
Purchase #6	$190.32	10.374%	$210.0638	$210.06	$210.05	$210.10
Purchase #7	$217.60	6.758%	$232.3054	$232.31	$232.30	$232.30
7 purchase totals =	$899.67		$974.6399	$974.64	$974.55	$974.70