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	$131.59	11.653%	$146.9242	$146.92	$146.90	$146.90
Purchase #2	$136.76	6.637%	$145.8368	$145.84	$145.85	$145.80
Purchase #3	$151.54	8.373%	$164.2284	$164.23	$164.25	$164.20
Purchase #4	$123.42	3.598%	$127.8607	$127.86	$127.85	$127.90
Purchase #5	$243.39	7.406%	$261.4155	$261.42	$261.40	$261.40
Purchase #6	$118.35	13.440%	$134.2562	$134.26	$134.25	$134.30
Purchase #7	$72.75	11.171%	$80.8769	$80.88	$80.90	$80.90
7 purchase totals =	$977.80		$1,061.3987	$1,061.41	$1,061.40	$1,061.40