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	$144.69	7.676%	$155.7964	$155.80	$155.80	$155.80
Purchase #2	$72.42	11.838%	$80.9931	$80.99	$81.00	$81.00
Purchase #3	$245.31	10.596%	$271.303	$271.30	$271.30	$271.30
Purchase #4	$82.43	3.489%	$85.306	$85.31	$85.30	$85.30
Purchase #5	$159.53	5.827%	$168.8258	$168.83	$168.85	$168.80
Purchase #6	$229.63	13.457%	$260.5313	$260.53	$260.55	$260.50
Purchase #7	$74.70	10.627%	$82.6384	$82.64	$82.65	$82.60
7 purchase totals =	$1,008.71		$1,105.3940	$1,105.40	$1,105.45	$1,105.30