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	$226.37	6.653%	$241.4304	$241.43	$241.45	$241.40
Purchase #2	$83.42	4.552%	$87.2173	$87.22	$87.20	$87.20
Purchase #3	$88.95	12.474%	$100.0456	$100.05	$100.05	$100.00
Purchase #4	$168.71	8.370%	$182.831	$182.83	$182.85	$182.80
Purchase #5	$54.49	6.236%	$57.888	$57.89	$57.90	$57.90
Purchase #6	$83.63	7.428%	$89.842	$89.84	$89.85	$89.80
Purchase #7	$68.84	10.649%	$76.1708	$76.17	$76.15	$76.20
7 purchase totals =	$774.41		$835.4251	$835.43	$835.45	$835.30