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	$162.53	7.238%	$174.2939	$174.29	$174.30	$174.30
Purchase #2	$232.78	9.673%	$255.2968	$255.30	$255.30	$255.30
Purchase #3	$126.31	12.315%	$141.8651	$141.87	$141.85	$141.90
Purchase #4	$121.60	12.693%	$137.0347	$137.03	$137.05	$137.00
Purchase #5	$229.84	11.276%	$255.7568	$255.76	$255.75	$255.80
Purchase #6	$202.30	13.309%	$229.2241	$229.22	$229.20	$229.20
Purchase #7	$22.53	10.320%	$24.8551	$24.86	$24.85	$24.90
7 purchase totals =	$1,097.89		$1,218.3265	$1,218.33	$1,218.30	$1,218.40