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	$92.34	10.341%	$101.8889	$101.89	$101.90	$101.90
Purchase #2	$160.26	13.438%	$181.7957	$181.80	$181.80	$181.80
Purchase #3	$148.80	12.571%	$167.5056	$167.51	$167.50	$167.50
Purchase #4	$72.78	12.300%	$81.7319	$81.73	$81.75	$81.70
Purchase #5	$206.84	10.533%	$228.6265	$228.63	$228.65	$228.60
Purchase #6	$155.30	13.855%	$176.8168	$176.82	$176.80	$176.80
Purchase #7	$161.37	6.137%	$171.2733	$171.27	$171.25	$171.30
7 purchase totals =	$997.69		$1,109.6387	$1,109.65	$1,109.65	$1,109.60