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	$13.29	6.385%	$14.1386	$14.14	$14.15	$14.10
Purchase #2	$75.69	8.391%	$82.0411	$82.04	$82.05	$82.00
Purchase #3	$216.81	3.121%	$223.5766	$223.58	$223.60	$223.60
Purchase #4	$19.32	7.609%	$20.7901	$20.79	$20.80	$20.80
Purchase #5	$77.43	6.286%	$82.2972	$82.30	$82.30	$82.30
Purchase #6	$81.73	9.277%	$89.3121	$89.31	$89.30	$89.30
Purchase #7	$243.94	6.401%	$259.5546	$259.55	$259.55	$259.60
7 purchase totals =	$728.21		$771.7103	$771.71	$771.75	$771.70