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	$176.55	4.423%	$184.3588	$184.36	$184.35	$184.40
Purchase #2	$231.84	11.543%	$258.6013	$258.60	$258.60	$258.60
Purchase #3	$87.30	11.702%	$97.5158	$97.52	$97.50	$97.50
Purchase #4	$88.69	6.604%	$94.5471	$94.55	$94.55	$94.50
Purchase #5	$92.92	9.194%	$101.4631	$101.46	$101.45	$101.50
Purchase #6	$94.48	11.524%	$105.3679	$105.37	$105.35	$105.40
Purchase #7	$92.84	8.256%	$100.5049	$100.50	$100.50	$100.50
7 purchase totals =	$864.62		$942.3589	$942.36	$942.30	$942.40