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	$94.75	11.268%	$105.4264	$105.43	$105.45	$105.40
Purchase #2	$126.96	8.410%	$137.6373	$137.64	$137.65	$137.60
Purchase #3	$213.26	4.757%	$223.4048	$223.40	$223.40	$223.40
Purchase #4	$169.57	10.693%	$187.7021	$187.70	$187.70	$187.70
Purchase #5	$25.86	5.468%	$27.274	$27.27	$27.25	$27.30
Purchase #6	$59.92	11.398%	$66.7497	$66.75	$66.75	$66.70
Purchase #7	$102.43	8.668%	$111.3086	$111.31	$111.30	$111.30
7 purchase totals =	$792.75		$859.5029	$859.50	$859.50	$859.40