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	$80.97	10.275%	$89.2897	$89.29	$89.30	$89.30
Purchase #2	$164.51	13.676%	$187.0084	$187.01	$187.00	$187.00
Purchase #3	$32.80	11.418%	$36.5451	$36.55	$36.55	$36.50
Purchase #4	$209.31	11.273%	$232.9055	$232.91	$232.90	$232.90
Purchase #5	$222.27	10.556%	$245.7328	$245.73	$245.75	$245.70
Purchase #6	$169.61	6.538%	$180.6991	$180.70	$180.70	$180.70
Purchase #7	$65.87	8.610%	$71.5414	$71.54	$71.55	$71.50
7 purchase totals =	$945.34		$1,043.7220	$1,043.73	$1,043.75	$1,043.60