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	$76.71	12.632%	$86.4	$86.40	$86.40	$86.40
Purchase #2	$217.87	5.815%	$230.5391	$230.54	$230.55	$230.50
Purchase #3	$23.64	11.331%	$26.3186	$26.32	$26.30	$26.30
Purchase #4	$91.58	4.284%	$95.5033	$95.50	$95.50	$95.50
Purchase #5	$98.90	13.569%	$112.3197	$112.32	$112.30	$112.30
Purchase #6	$193.86	12.332%	$217.7668	$217.77	$217.75	$217.80
Purchase #7	$234.40	5.755%	$247.8897	$247.89	$247.90	$247.90
7 purchase totals =	$936.96		$1,016.7372	$1,016.74	$1,016.70	$1,016.70