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	$104.37	4.602%	$109.1731	$109.17	$109.15	$109.20
Purchase #2	$42.31	5.309%	$44.5562	$44.56	$44.55	$44.60
Purchase #3	$83.37	6.842%	$89.0742	$89.07	$89.05	$89.10
Purchase #4	$68.65	13.322%	$77.7956	$77.80	$77.80	$77.80
Purchase #5	$240.93	5.462%	$254.0896	$254.09	$254.10	$254.10
Purchase #6	$66.79	6.747%	$71.2963	$71.30	$71.30	$71.30
Purchase #7	$52.35	10.429%	$57.8096	$57.81	$57.80	$57.80
7 purchase totals =	$658.77		$703.7946	$703.80	$703.75	$703.90