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	$44.99	3.159%	$46.4112	$46.41	$46.40	$46.40
Purchase #2	$199.52	8.315%	$216.1101	$216.11	$216.10	$216.10
Purchase #3	$94.61	9.581%	$103.6746	$103.67	$103.65	$103.70
Purchase #4	$137.32	5.806%	$145.2928	$145.29	$145.30	$145.30
Purchase #5	$117.27	7.657%	$126.2494	$126.25	$126.25	$126.20
Purchase #6	$38.34	10.298%	$42.2883	$42.29	$42.30	$42.30
Purchase #7	$73.41	9.493%	$80.3788	$80.38	$80.40	$80.40
7 purchase totals =	$705.46		$760.4052	$760.40	$760.40	$760.40