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	$180.60	9.778%	$198.2591	$198.26	$198.25	$198.30
Purchase #2	$175.36	13.160%	$198.4374	$198.44	$198.45	$198.40
Purchase #3	$78.59	5.625%	$83.0107	$83.01	$83.00	$83.00
Purchase #4	$83.88	10.407%	$92.6094	$92.61	$92.60	$92.60
Purchase #5	$95.79	13.823%	$109.0311	$109.03	$109.05	$109.00
Purchase #6	$57.29	11.155%	$63.6807	$63.68	$63.70	$63.70
Purchase #7	$181.90	7.856%	$196.1901	$196.19	$196.20	$196.20
7 purchase totals =	$853.41		$941.2185	$941.22	$941.25	$941.20