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	$195.46	10.257%	$215.5083	$215.51	$215.50	$215.50
Purchase #2	$200.97	6.239%	$213.5085	$213.51	$213.50	$213.50
Purchase #3	$104.38	5.234%	$109.8432	$109.84	$109.85	$109.80
Purchase #4	$156.90	6.568%	$167.2052	$167.21	$167.20	$167.20
Purchase #5	$225.87	6.498%	$240.547	$240.55	$240.55	$240.50
Purchase #6	$11.72	10.802%	$12.986	$12.99	$13.00	$13.00
Purchase #7	$134.79	11.299%	$150.0199	$150.02	$150.00	$150.00
7 purchase totals =	$1,030.09		$1,109.6181	$1,109.63	$1,109.60	$1,109.50