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	$219.98	13.418%	$249.4969	$249.50	$249.50	$249.50
Purchase #2	$31.30	7.253%	$33.5702	$33.57	$33.55	$33.60
Purchase #3	$119.82	4.649%	$125.3904	$125.39	$125.40	$125.40
Purchase #4	$196.31	5.397%	$206.9049	$206.90	$206.90	$206.90
Purchase #5	$41.30	3.254%	$42.6439	$42.64	$42.65	$42.60
Purchase #6	$205.38	11.589%	$229.1815	$229.18	$229.20	$229.20
Purchase #7	$56.89	3.718%	$59.0052	$59.01	$59.00	$59.00
7 purchase totals =	$870.98		$946.1930	$946.19	$946.20	$946.20