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	$230.59	12.554%	$259.5383	$259.54	$259.55	$259.50
Purchase #2	$65.45	3.139%	$67.5045	$67.50	$67.50	$67.50
Purchase #3	$75.76	5.237%	$79.7276	$79.73	$79.75	$79.70
Purchase #4	$175.92	8.629%	$191.1001	$191.10	$191.10	$191.10
Purchase #5	$42.86	12.119%	$48.0542	$48.05	$48.05	$48.10
Purchase #6	$14.91	13.337%	$16.8985	$16.90	$16.90	$16.90
Purchase #7	$40.78	4.570%	$42.6436	$42.64	$42.65	$42.60
7 purchase totals =	$646.27		$705.4668	$705.46	$705.50	$705.40