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	$172.38	10.228%	$190.011	$190.01	$190.00	$190.00
Purchase #2	$202.93	7.252%	$217.6465	$217.65	$217.65	$217.60
Purchase #3	$86.92	10.775%	$96.2856	$96.29	$96.30	$96.30
Purchase #4	$56.53	4.504%	$59.0761	$59.08	$59.10	$59.10
Purchase #5	$160.43	4.142%	$167.075	$167.08	$167.10	$167.10
Purchase #6	$36.74	5.432%	$38.7357	$38.74	$38.75	$38.70
Purchase #7	$65.96	8.536%	$71.5903	$71.59	$71.60	$71.60
7 purchase totals =	$781.89		$840.4202	$840.44	$840.50	$840.40