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	$100.59	6.840%	$107.4704	$107.47	$107.45	$107.50
Purchase #2	$162.48	4.534%	$169.8468	$169.85	$169.85	$169.80
Purchase #3	$194.25	13.718%	$220.8972	$220.90	$220.90	$220.90
Purchase #4	$201.89	10.609%	$223.3085	$223.31	$223.30	$223.30
Purchase #5	$148.46	11.654%	$165.7615	$165.76	$165.75	$165.80
Purchase #6	$160.34	4.685%	$167.8519	$167.85	$167.85	$167.90
Purchase #7	$105.60	7.241%	$113.2465	$113.25	$113.25	$113.20
7 purchase totals =	$1,073.61		$1,168.3828	$1,168.39	$1,168.35	$1,168.40