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	$37.34	3.466%	$38.6342	$38.63	$38.65	$38.60
Purchase #2	$152.60	6.394%	$162.3572	$162.36	$162.35	$162.40
Purchase #3	$78.55	13.676%	$89.2925	$89.29	$89.30	$89.30
Purchase #4	$173.56	4.287%	$181.0005	$181.00	$181.00	$181.00
Purchase #5	$35.55	6.354%	$37.8088	$37.81	$37.80	$37.80
Purchase #6	$182.92	9.531%	$200.3541	$200.35	$200.35	$200.40
Purchase #7	$217.81	3.640%	$225.7383	$225.74	$225.75	$225.70
7 purchase totals =	$878.33		$935.1856	$935.18	$935.20	$935.20