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	$114.75	3.740%	$119.0417	$119.04	$119.05	$119.00
Purchase #2	$130.79	5.215%	$137.6107	$137.61	$137.60	$137.60
Purchase #3	$90.54	13.145%	$102.4415	$102.44	$102.45	$102.40
Purchase #4	$126.47	5.478%	$133.398	$133.40	$133.40	$133.40
Purchase #5	$86.56	3.793%	$89.8432	$89.84	$89.85	$89.80
Purchase #6	$227.78	6.823%	$243.3214	$243.32	$243.30	$243.30
Purchase #7	$86.33	7.142%	$92.4957	$92.50	$92.50	$92.50
7 purchase totals =	$863.22		$918.1522	$918.15	$918.15	$918.00