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	$29.96	12.132%	$33.5947	$33.59	$33.60	$33.60
Purchase #2	$72.36	7.525%	$77.8051	$77.81	$77.80	$77.80
Purchase #3	$43.31	4.374%	$45.2044	$45.20	$45.20	$45.20
Purchase #4	$63.82	6.675%	$68.08	$68.08	$68.10	$68.10
Purchase #5	$35.75	11.726%	$39.942	$39.94	$39.95	$39.90
Purchase #6	$101.53	11.441%	$113.146	$113.15	$113.15	$113.10
Purchase #7	$80.90	10.663%	$89.5264	$89.53	$89.55	$89.50
7 purchase totals =	$427.63		$467.2986	$467.30	$467.35	$467.20