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	$241.69	6.295%	$256.9044	$256.90	$256.90	$256.90
Purchase #2	$72.43	7.133%	$77.5964	$77.60	$77.60	$77.60
Purchase #3	$155.91	6.626%	$166.2406	$166.24	$166.25	$166.20
Purchase #4	$110.94	4.597%	$116.0399	$116.04	$116.05	$116.00
Purchase #5	$237.80	11.108%	$264.2148	$264.21	$264.20	$264.20
Purchase #6	$82.29	7.480%	$88.4453	$88.45	$88.45	$88.40
Purchase #7	$157.38	10.144%	$173.3446	$173.34	$173.35	$173.30
7 purchase totals =	$1,058.44		$1,142.7860	$1,142.78	$1,142.80	$1,142.60