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	$72.35	4.407%	$75.5385	$75.54	$75.55	$75.50
Purchase #2	$191.60	13.177%	$216.8471	$216.85	$216.85	$216.80
Purchase #3	$165.92	7.831%	$178.9132	$178.91	$178.90	$178.90
Purchase #4	$200.72	9.406%	$219.5997	$219.60	$219.60	$219.60
Purchase #5	$215.55	11.557%	$240.4611	$240.46	$240.45	$240.50
Purchase #6	$186.92	7.516%	$200.9689	$200.97	$200.95	$201.00
Purchase #7	$139.64	11.636%	$155.8885	$155.89	$155.90	$155.90
7 purchase totals =	$1,172.70		$1,288.2170	$1,288.22	$1,288.20	$1,288.20