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	$233.62	12.354%	$262.4814	$262.48	$262.50	$262.50
Purchase #2	$72.49	10.821%	$80.3341	$80.33	$80.35	$80.30
Purchase #3	$142.70	9.670%	$156.4991	$156.50	$156.50	$156.50
Purchase #4	$216.68	11.556%	$241.7195	$241.72	$241.70	$241.70
Purchase #5	$85.28	7.308%	$91.5123	$91.51	$91.50	$91.50
Purchase #6	$31.45	7.234%	$33.7251	$33.73	$33.75	$33.70
Purchase #7	$199.35	12.581%	$224.4302	$224.43	$224.45	$224.40
7 purchase totals =	$981.57		$1,090.7017	$1,090.70	$1,090.75	$1,090.60