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	$134.40	13.797%	$152.9432	$152.94	$152.95	$152.90
Purchase #2	$52.81	13.272%	$59.8189	$59.82	$59.80	$59.80
Purchase #3	$41.82	9.581%	$45.8268	$45.83	$45.85	$45.80
Purchase #4	$76.44	10.346%	$84.3485	$84.35	$84.35	$84.30
Purchase #5	$82.96	9.530%	$90.8661	$90.87	$90.85	$90.90
Purchase #6	$232.86	10.104%	$256.3882	$256.39	$256.40	$256.40
Purchase #7	$193.81	12.172%	$217.4006	$217.40	$217.40	$217.40
7 purchase totals =	$815.10		$907.5923	$907.60	$907.60	$907.50