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	$207.97	4.256%	$216.8212	$216.82	$216.80	$216.80
Purchase #2	$131.27	4.863%	$137.6537	$137.65	$137.65	$137.70
Purchase #3	$126.66	12.711%	$142.7598	$142.76	$142.75	$142.80
Purchase #4	$180.81	5.304%	$190.4002	$190.40	$190.40	$190.40
Purchase #5	$56.31	6.542%	$59.9938	$59.99	$60.00	$60.00
Purchase #6	$75.90	12.375%	$85.2926	$85.29	$85.30	$85.30
Purchase #7	$79.54	13.494%	$90.2731	$90.27	$90.25	$90.30
7 purchase totals =	$858.46		$923.1944	$923.18	$923.15	$923.30