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	$147.78	3.245%	$152.5755	$152.58	$152.60	$152.60
Purchase #2	$33.30	13.518%	$37.8015	$37.80	$37.80	$37.80
Purchase #3	$117.69	4.749%	$123.2791	$123.28	$123.30	$123.30
Purchase #4	$19.84	8.338%	$21.4943	$21.49	$21.50	$21.50
Purchase #5	$164.61	10.441%	$181.7969	$181.80	$181.80	$181.80
Purchase #6	$246.67	9.701%	$270.5995	$270.60	$270.60	$270.60
Purchase #7	$158.32	10.217%	$174.4956	$174.50	$174.50	$174.50
7 purchase totals =	$888.21		$962.0424	$962.05	$962.10	$962.10