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	$76.87	12.134%	$86.1974	$86.20	$86.20	$86.20
Purchase #2	$217.68	9.483%	$238.3226	$238.32	$238.30	$238.30
Purchase #3	$99.78	9.487%	$109.2461	$109.25	$109.25	$109.20
Purchase #4	$233.41	12.561%	$262.7286	$262.73	$262.75	$262.70
Purchase #5	$195.36	4.223%	$203.6101	$203.61	$203.60	$203.60
Purchase #6	$197.64	13.136%	$223.602	$223.60	$223.60	$223.60
Purchase #7	$72.38	11.367%	$80.6074	$80.61	$80.60	$80.60
7 purchase totals =	$1,093.12		$1,204.3142	$1,204.32	$1,204.30	$1,204.20