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	$195.41	4.578%	$204.3559	$204.36	$204.35	$204.40
Purchase #2	$88.88	3.456%	$91.9517	$91.95	$91.95	$92.00
Purchase #3	$36.36	11.650%	$40.5959	$40.60	$40.60	$40.60
Purchase #4	$103.31	6.215%	$109.7307	$109.73	$109.75	$109.70
Purchase #5	$147.60	7.780%	$159.0833	$159.08	$159.10	$159.10
Purchase #6	$230.83	10.555%	$255.1941	$255.19	$255.20	$255.20
Purchase #7	$107.37	3.397%	$111.0174	$111.02	$111.00	$111.00
7 purchase totals =	$909.76		$971.9290	$971.93	$971.95	$972.00