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	$165.95	6.596%	$176.8961	$176.90	$176.90	$176.90
Purchase #2	$182.90	3.604%	$189.4917	$189.49	$189.50	$189.50
Purchase #3	$11.85	4.438%	$12.3759	$12.38	$12.40	$12.40
Purchase #4	$88.73	12.292%	$99.6367	$99.64	$99.65	$99.60
Purchase #5	$153.85	11.478%	$171.5089	$171.51	$171.50	$171.50
Purchase #6	$234.47	4.509%	$245.0423	$245.04	$245.05	$245.00
Purchase #7	$236.95	7.455%	$254.6146	$254.61	$254.60	$254.60
7 purchase totals =	$1,074.70		$1,149.5662	$1,149.57	$1,149.60	$1,149.50