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	$74.50	11.402%	$82.9945	$82.99	$83.00	$83.00
Purchase #2	$199.86	6.432%	$212.715	$212.72	$212.70	$212.70
Purchase #3	$24.51	13.453%	$27.8073	$27.81	$27.80	$27.80
Purchase #4	$50.27	4.844%	$52.7051	$52.71	$52.70	$52.70
Purchase #5	$179.49	9.627%	$196.7695	$196.77	$196.75	$196.80
Purchase #6	$238.90	8.567%	$259.3666	$259.37	$259.35	$259.40
Purchase #7	$98.91	6.746%	$105.5825	$105.58	$105.60	$105.60
7 purchase totals =	$866.44		$937.9405	$937.95	$937.90	$938.00