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	$156.70	4.253%	$163.3645	$163.36	$163.35	$163.40
Purchase #2	$74.63	5.360%	$78.6302	$78.63	$78.65	$78.60
Purchase #3	$236.70	12.789%	$266.9716	$266.97	$266.95	$267.00
Purchase #4	$171.55	7.457%	$184.3425	$184.34	$184.35	$184.30
Purchase #5	$73.61	6.673%	$78.522	$78.52	$78.50	$78.50
Purchase #6	$35.42	5.451%	$37.3507	$37.35	$37.35	$37.40
Purchase #7	$95.87	4.188%	$99.885	$99.89	$99.90	$99.90
7 purchase totals =	$844.48		$909.0665	$909.06	$909.05	$909.10