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	$208.32	5.467%	$219.7089	$219.71	$219.70	$219.70
Purchase #2	$96.55	9.638%	$105.8555	$105.86	$105.85	$105.90
Purchase #3	$87.90	11.649%	$98.1395	$98.14	$98.15	$98.10
Purchase #4	$154.44	12.763%	$174.1512	$174.15	$174.15	$174.20
Purchase #5	$72.70	12.327%	$81.6617	$81.66	$81.65	$81.70
Purchase #6	$178.92	9.872%	$196.583	$196.58	$196.60	$196.60
Purchase #7	$108.34	11.223%	$120.499	$120.50	$120.50	$120.50
7 purchase totals =	$907.17		$996.5988	$996.60	$996.60	$996.70