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	$201.31	10.705%	$222.8602	$222.86	$222.85	$222.90
Purchase #2	$172.27	9.849%	$189.2369	$189.24	$189.25	$189.20
Purchase #3	$232.30	7.238%	$249.1139	$249.11	$249.10	$249.10
Purchase #4	$173.26	13.240%	$196.1996	$196.20	$196.20	$196.20
Purchase #5	$13.47	9.872%	$14.7998	$14.80	$14.80	$14.80
Purchase #6	$35.80	3.812%	$37.1647	$37.16	$37.15	$37.20
Purchase #7	$152.36	4.333%	$158.9618	$158.96	$158.95	$159.00
7 purchase totals =	$980.77		$1,068.3369	$1,068.33	$1,068.30	$1,068.40