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	$222.42	8.576%	$241.4947	$241.49	$241.50	$241.50
Purchase #2	$28.86	12.468%	$32.4583	$32.46	$32.45	$32.50
Purchase #3	$17.36	5.382%	$18.2943	$18.29	$18.30	$18.30
Purchase #4	$250.94	3.856%	$260.6162	$260.62	$260.60	$260.60
Purchase #5	$35.59	6.559%	$37.9243	$37.92	$37.90	$37.90
Purchase #6	$55.48	13.413%	$62.9215	$62.92	$62.90	$62.90
Purchase #7	$180.71	6.209%	$191.9303	$191.93	$191.95	$191.90
7 purchase totals =	$791.36		$845.6396	$845.63	$845.60	$845.60