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	$176.37	8.394%	$191.1745	$191.17	$191.15	$191.20
Purchase #2	$148.66	9.273%	$162.4452	$162.45	$162.45	$162.40
Purchase #3	$130.61	4.780%	$136.8532	$136.85	$136.85	$136.90
Purchase #4	$150.62	11.573%	$168.0513	$168.05	$168.05	$168.10
Purchase #5	$31.64	6.431%	$33.6748	$33.67	$33.65	$33.70
Purchase #6	$105.48	11.792%	$117.9182	$117.92	$117.90	$117.90
Purchase #7	$213.62	3.871%	$221.8892	$221.89	$221.90	$221.90
7 purchase totals =	$957.00		$1,032.0064	$1,032.00	$1,031.95	$1,032.10