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	$82.70	5.523%	$87.2675	$87.27	$87.25	$87.30
Purchase #2	$31.84	11.653%	$35.5503	$35.55	$35.55	$35.60
Purchase #3	$119.78	7.477%	$128.736	$128.74	$128.75	$128.70
Purchase #4	$20.91	4.673%	$21.8871	$21.89	$21.90	$21.90
Purchase #5	$97.99	11.786%	$109.5391	$109.54	$109.55	$109.50
Purchase #6	$43.39	11.772%	$48.4979	$48.50	$48.50	$48.50
Purchase #7	$56.51	5.620%	$59.6859	$59.69	$59.70	$59.70
7 purchase totals =	$453.12		$491.1638	$491.18	$491.20	$491.20