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	$164.84	10.539%	$182.2125	$182.21	$182.20	$182.20
Purchase #2	$74.74	11.787%	$83.5496	$83.55	$83.55	$83.50
Purchase #3	$54.77	6.629%	$58.4007	$58.40	$58.40	$58.40
Purchase #4	$129.56	11.285%	$144.1808	$144.18	$144.20	$144.20
Purchase #5	$219.60	12.708%	$247.5068	$247.51	$247.50	$247.50
Purchase #6	$117.43	8.515%	$127.4292	$127.43	$127.45	$127.40
Purchase #7	$221.60	5.257%	$233.2495	$233.25	$233.25	$233.20
7 purchase totals =	$982.54		$1,076.5291	$1,076.53	$1,076.55	$1,076.40