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	$208.50	8.582%	$226.3935	$226.39	$226.40	$226.40
Purchase #2	$38.69	9.439%	$42.3419	$42.34	$42.35	$42.30
Purchase #3	$99.66	3.846%	$103.4929	$103.49	$103.50	$103.50
Purchase #4	$117.67	8.568%	$127.752	$127.75	$127.75	$127.80
Purchase #5	$77.90	3.797%	$80.8579	$80.86	$80.85	$80.90
Purchase #6	$154.59	4.266%	$161.1848	$161.18	$161.20	$161.20
Purchase #7	$58.63	12.404%	$65.9025	$65.90	$65.90	$65.90
7 purchase totals =	$755.64		$807.9255	$807.91	$807.95	$808.00