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	$247.56	6.437%	$263.4954	$263.50	$263.50	$263.50
Purchase #2	$113.89	5.619%	$120.2895	$120.29	$120.30	$120.30
Purchase #3	$108.30	5.175%	$113.9045	$113.90	$113.90	$113.90
Purchase #4	$97.83	13.514%	$111.0507	$111.05	$111.05	$111.10
Purchase #5	$127.32	6.783%	$135.9561	$135.96	$135.95	$136.00
Purchase #6	$131.68	11.707%	$147.0958	$147.10	$147.10	$147.10
Purchase #7	$182.91	4.264%	$190.7093	$190.71	$190.70	$190.70
7 purchase totals =	$1,009.49		$1,082.5013	$1,082.51	$1,082.50	$1,082.60