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	$41.84	4.368%	$43.6676	$43.67	$43.65	$43.70
Purchase #2	$206.62	4.269%	$215.4406	$215.44	$215.45	$215.40
Purchase #3	$26.85	11.596%	$29.9635	$29.96	$29.95	$30.00
Purchase #4	$40.37	13.815%	$45.9471	$45.95	$45.95	$45.90
Purchase #5	$86.73	3.359%	$89.6433	$89.64	$89.65	$89.60
Purchase #6	$93.47	13.121%	$105.7342	$105.73	$105.75	$105.70
Purchase #7	$224.96	12.602%	$253.3095	$253.31	$253.30	$253.30
7 purchase totals =	$720.84		$783.7058	$783.70	$783.70	$783.60