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	$56.58	4.703%	$59.241	$59.24	$59.25	$59.20
Purchase #2	$247.70	8.819%	$269.5447	$269.54	$269.55	$269.50
Purchase #3	$95.66	4.177%	$99.6557	$99.66	$99.65	$99.70
Purchase #4	$123.30	8.611%	$133.9174	$133.92	$133.90	$133.90
Purchase #5	$53.78	10.395%	$59.3704	$59.37	$59.35	$59.40
Purchase #6	$29.42	8.324%	$31.8689	$31.87	$31.85	$31.90
Purchase #7	$174.33	8.248%	$188.7087	$188.71	$188.70	$188.70
7 purchase totals =	$780.77		$842.3068	$842.31	$842.25	$842.30