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	$139.69	7.605%	$150.3134	$150.31	$150.30	$150.30
Purchase #2	$134.65	9.754%	$147.7838	$147.78	$147.80	$147.80
Purchase #3	$55.67	6.435%	$59.2524	$59.25	$59.25	$59.30
Purchase #4	$160.45	12.817%	$181.0149	$181.01	$181.00	$181.00
Purchase #5	$156.50	9.838%	$171.8965	$171.90	$171.90	$171.90
Purchase #6	$12.64	13.175%	$14.3053	$14.31	$14.30	$14.30
Purchase #7	$134.86	4.331%	$140.7008	$140.70	$140.70	$140.70
7 purchase totals =	$794.46		$865.2671	$865.26	$865.25	$865.30