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	$211.62	10.507%	$233.8549	$233.85	$233.85	$233.90
Purchase #2	$171.52	9.792%	$188.3152	$188.32	$188.30	$188.30
Purchase #3	$118.84	12.430%	$133.6118	$133.61	$133.60	$133.60
Purchase #4	$61.90	7.642%	$66.6304	$66.63	$66.65	$66.60
Purchase #5	$62.42	3.228%	$64.4349	$64.43	$64.45	$64.40
Purchase #6	$41.54	3.260%	$42.8942	$42.89	$42.90	$42.90
Purchase #7	$221.99	9.351%	$242.7483	$242.75	$242.75	$242.70
7 purchase totals =	$889.83		$972.4897	$972.48	$972.50	$972.40