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	$78.73	9.254%	$86.0157	$86.02	$86.00	$86.00
Purchase #2	$167.88	3.223%	$173.2908	$173.29	$173.30	$173.30
Purchase #3	$213.96	4.441%	$223.462	$223.46	$223.45	$223.50
Purchase #4	$113.71	5.448%	$119.9049	$119.90	$119.90	$119.90
Purchase #5	$225.37	3.396%	$233.0236	$233.02	$233.00	$233.00
Purchase #6	$95.30	11.560%	$106.3167	$106.32	$106.30	$106.30
Purchase #7	$93.78	11.578%	$104.6378	$104.64	$104.65	$104.60
7 purchase totals =	$988.73		$1,046.6515	$1,046.65	$1,046.60	$1,046.60