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	$208.83	12.233%	$234.3762	$234.38	$234.40	$234.40
Purchase #2	$116.78	7.796%	$125.8842	$125.88	$125.90	$125.90
Purchase #3	$112.45	9.801%	$123.4712	$123.47	$123.45	$123.50
Purchase #4	$192.47	12.339%	$216.2189	$216.22	$216.20	$216.20
Purchase #5	$52.50	10.524%	$58.0251	$58.03	$58.05	$58.00
Purchase #6	$200.44	11.263%	$223.0156	$223.02	$223.00	$223.00
Purchase #7	$91.70	4.526%	$95.8503	$95.85	$95.85	$95.90
7 purchase totals =	$975.17		$1,076.8415	$1,076.85	$1,076.85	$1,076.90