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	$136.73	4.381%	$142.7201	$142.72	$142.70	$142.70
Purchase #2	$105.52	3.128%	$108.8207	$108.82	$108.80	$108.80
Purchase #3	$195.95	13.324%	$222.0584	$222.06	$222.05	$222.10
Purchase #4	$197.93	6.264%	$210.3283	$210.33	$210.35	$210.30
Purchase #5	$226.94	11.870%	$253.8778	$253.88	$253.90	$253.90
Purchase #6	$43.71	6.759%	$46.6644	$46.66	$46.65	$46.70
Purchase #7	$100.29	11.450%	$111.7732	$111.77	$111.75	$111.80
7 purchase totals =	$1,007.07		$1,096.2429	$1,096.24	$1,096.20	$1,096.30