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	$31.59	5.386%	$33.2914	$33.29	$33.30	$33.30
Purchase #2	$9.73	11.153%	$10.8152	$10.82	$10.80	$10.80
Purchase #3	$106.44	6.715%	$113.5874	$113.59	$113.60	$113.60
Purchase #4	$30.27	9.707%	$33.2083	$33.21	$33.20	$33.20
Purchase #5	$56.36	3.352%	$58.2492	$58.25	$58.25	$58.20
Purchase #6	$175.35	4.167%	$182.6568	$182.66	$182.65	$182.70
Purchase #7	$183.93	6.867%	$196.5605	$196.56	$196.55	$196.60
7 purchase totals =	$593.67		$628.3688	$628.38	$628.35	$628.40