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	$224.55	10.397%	$247.8965	$247.90	$247.90	$247.90
Purchase #2	$69.42	12.492%	$78.0919	$78.09	$78.10	$78.10
Purchase #3	$100.65	6.506%	$107.1983	$107.20	$107.20	$107.20
Purchase #4	$150.37	6.406%	$160.0027	$160.00	$160.00	$160.00
Purchase #5	$64.89	11.668%	$72.4614	$72.46	$72.45	$72.50
Purchase #6	$134.53	12.764%	$151.7014	$151.70	$151.70	$151.70
Purchase #7	$29.36	6.227%	$31.1882	$31.19	$31.20	$31.20
7 purchase totals =	$773.77		$848.5404	$848.54	$848.55	$848.60