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	$49.38	6.440%	$52.5601	$52.56	$52.55	$52.60
Purchase #2	$71.73	12.108%	$80.4151	$80.42	$80.40	$80.40
Purchase #3	$114.78	11.333%	$127.788	$127.79	$127.80	$127.80
Purchase #4	$46.44	9.144%	$50.6865	$50.69	$50.70	$50.70
Purchase #5	$36.86	3.120%	$38.01	$38.01	$38.00	$38.00
Purchase #6	$108.30	8.863%	$117.8986	$117.90	$117.90	$117.90
Purchase #7	$36.77	7.794%	$39.6359	$39.64	$39.65	$39.60
7 purchase totals =	$464.26		$506.9942	$507.01	$507.00	$507.00