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	$56.95	6.395%	$60.592	$60.59	$60.60	$60.60
Purchase #2	$149.69	12.196%	$167.9462	$167.95	$167.95	$167.90
Purchase #3	$75.39	4.284%	$78.6197	$78.62	$78.60	$78.60
Purchase #4	$231.34	4.395%	$241.5074	$241.51	$241.50	$241.50
Purchase #5	$196.66	8.567%	$213.5079	$213.51	$213.50	$213.50
Purchase #6	$244.32	7.539%	$262.7393	$262.74	$262.75	$262.70
Purchase #7	$148.93	10.457%	$164.5036	$164.50	$164.50	$164.50
7 purchase totals =	$1,103.28		$1,189.4161	$1,189.42	$1,189.40	$1,189.30