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	$231.61	12.644%	$260.8948	$260.89	$260.90	$260.90
Purchase #2	$142.82	6.509%	$152.1162	$152.12	$152.10	$152.10
Purchase #3	$223.72	9.164%	$244.2217	$244.22	$244.20	$244.20
Purchase #4	$146.54	6.810%	$156.5194	$156.52	$156.50	$156.50
Purchase #5	$103.94	3.647%	$107.7307	$107.73	$107.75	$107.70
Purchase #6	$186.32	7.603%	$200.4859	$200.49	$200.50	$200.50
Purchase #7	$159.45	13.443%	$180.8849	$180.88	$180.90	$180.90
7 purchase totals =	$1,194.40		$1,302.8536	$1,302.85	$1,302.85	$1,302.80