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	$147.56	11.422%	$164.4143	$164.41	$164.40	$164.40
Purchase #2	$9.89	8.303%	$10.7112	$10.71	$10.70	$10.70
Purchase #3	$234.89	12.730%	$264.7915	$264.79	$264.80	$264.80
Purchase #4	$91.78	5.474%	$96.804	$96.80	$96.80	$96.80
Purchase #5	$59.74	4.196%	$62.2467	$62.25	$62.25	$62.20
Purchase #6	$23.94	3.698%	$24.8253	$24.83	$24.85	$24.80
Purchase #7	$108.32	5.535%	$114.3155	$114.32	$114.30	$114.30
7 purchase totals =	$676.12		$738.1085	$738.11	$738.10	$738.00