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	$208.57	9.542%	$228.4717	$228.47	$228.45	$228.50
Purchase #2	$170.80	6.121%	$181.2547	$181.25	$181.25	$181.30
Purchase #3	$234.48	10.248%	$258.5095	$258.51	$258.50	$258.50
Purchase #4	$74.85	11.160%	$83.2033	$83.20	$83.20	$83.20
Purchase #5	$123.36	3.274%	$127.3988	$127.40	$127.40	$127.40
Purchase #6	$165.78	12.394%	$186.3268	$186.33	$186.35	$186.30
Purchase #7	$205.85	11.610%	$229.7492	$229.75	$229.75	$229.70
7 purchase totals =	$1,183.69		$1,294.9140	$1,294.91	$1,294.90	$1,294.90