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	$62.31	8.134%	$67.3783	$67.38	$67.40	$67.40
Purchase #2	$101.73	3.800%	$105.5957	$105.60	$105.60	$105.60
Purchase #3	$195.59	6.402%	$208.1117	$208.11	$208.10	$208.10
Purchase #4	$217.77	6.303%	$231.496	$231.50	$231.50	$231.50
Purchase #5	$139.66	13.674%	$158.7571	$158.76	$158.75	$158.80
Purchase #6	$93.45	4.597%	$97.7459	$97.75	$97.75	$97.70
Purchase #7	$186.78	6.570%	$199.0514	$199.05	$199.05	$199.10
7 purchase totals =	$997.29		$1,068.1361	$1,068.15	$1,068.15	$1,068.20