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	$83.81	9.802%	$92.0251	$92.03	$92.05	$92.00
Purchase #2	$30.60	3.316%	$31.6147	$31.61	$31.60	$31.60
Purchase #3	$28.94	8.820%	$31.4925	$31.49	$31.50	$31.50
Purchase #4	$82.68	4.688%	$86.556	$86.56	$86.55	$86.60
Purchase #5	$199.28	8.131%	$215.4835	$215.48	$215.50	$215.50
Purchase #6	$230.80	8.112%	$249.5225	$249.52	$249.50	$249.50
Purchase #7	$143.66	5.711%	$151.8644	$151.86	$151.85	$151.90
7 purchase totals =	$799.77		$858.5587	$858.55	$858.55	$858.60