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	$172.57	10.402%	$190.5207	$190.52	$190.50	$190.50
Purchase #2	$184.38	9.824%	$202.4935	$202.49	$202.50	$202.50
Purchase #3	$210.77	10.308%	$232.4962	$232.50	$232.50	$232.50
Purchase #4	$53.68	10.147%	$59.1269	$59.13	$59.15	$59.10
Purchase #5	$142.30	5.545%	$150.1905	$150.19	$150.20	$150.20
Purchase #6	$91.87	12.477%	$103.3326	$103.33	$103.35	$103.30
Purchase #7	$208.84	10.798%	$231.3905	$231.39	$231.40	$231.40
7 purchase totals =	$1,064.41		$1,169.5509	$1,169.55	$1,169.60	$1,169.50