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	$226.62	11.814%	$253.3929	$253.39	$253.40	$253.40
Purchase #2	$41.44	7.338%	$44.4809	$44.48	$44.50	$44.50
Purchase #3	$83.61	7.865%	$90.1859	$90.19	$90.20	$90.20
Purchase #4	$182.35	12.817%	$205.7218	$205.72	$205.70	$205.70
Purchase #5	$38.83	8.793%	$42.2443	$42.24	$42.25	$42.20
Purchase #6	$78.25	5.628%	$82.6539	$82.65	$82.65	$82.70
Purchase #7	$25.56	6.862%	$27.3139	$27.31	$27.30	$27.30
7 purchase totals =	$676.66		$745.9936	$745.98	$746.00	$746.00