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	$102.85	8.127%	$111.2086	$111.21	$111.20	$111.20
Purchase #2	$21.49	3.711%	$22.2875	$22.29	$22.30	$22.30
Purchase #3	$100.81	6.809%	$107.6742	$107.67	$107.65	$107.70
Purchase #4	$78.88	4.268%	$82.2466	$82.25	$82.25	$82.20
Purchase #5	$81.43	13.792%	$92.6608	$92.66	$92.65	$92.70
Purchase #6	$84.39	11.813%	$94.359	$94.36	$94.35	$94.40
Purchase #7	$70.52	4.354%	$73.5904	$73.59	$73.60	$73.60
7 purchase totals =	$540.37		$584.0271	$584.03	$584.00	$584.10