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	$217.98	12.492%	$245.2101	$245.21	$245.20	$245.20
Purchase #2	$224.34	11.411%	$249.9394	$249.94	$249.95	$249.90
Purchase #3	$98.40	9.457%	$107.7057	$107.71	$107.70	$107.70
Purchase #4	$79.88	12.374%	$89.7644	$89.76	$89.75	$89.80
Purchase #5	$170.60	10.147%	$187.9108	$187.91	$187.90	$187.90
Purchase #6	$184.48	6.565%	$196.5911	$196.59	$196.60	$196.60
Purchase #7	$113.82	5.132%	$119.6612	$119.66	$119.65	$119.70
7 purchase totals =	$1,089.50		$1,196.7827	$1,196.78	$1,196.75	$1,196.80