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	$181.68	3.146%	$187.3957	$187.40	$187.40	$187.40
Purchase #2	$48.50	7.487%	$52.1312	$52.13	$52.15	$52.10
Purchase #3	$89.44	7.272%	$95.9441	$95.94	$95.95	$95.90
Purchase #4	$231.40	3.241%	$238.8997	$238.90	$238.90	$238.90
Purchase #5	$230.77	7.298%	$247.6116	$247.61	$247.60	$247.60
Purchase #6	$117.77	8.339%	$127.5908	$127.59	$127.60	$127.60
Purchase #7	$22.37	13.272%	$25.3389	$25.34	$25.35	$25.30
7 purchase totals =	$921.93		$974.9120	$974.91	$974.95	$974.80