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	$106.46	5.559%	$112.3781	$112.38	$112.40	$112.40
Purchase #2	$87.88	8.698%	$95.5238	$95.52	$95.50	$95.50
Purchase #3	$175.96	11.731%	$196.6019	$196.60	$196.60	$196.60
Purchase #4	$248.90	13.613%	$282.7828	$282.78	$282.80	$282.80
Purchase #5	$168.40	13.489%	$191.1155	$191.12	$191.10	$191.10
Purchase #6	$155.26	7.300%	$166.594	$166.59	$166.60	$166.60
Purchase #7	$174.95	3.766%	$181.5386	$181.54	$181.55	$181.50
7 purchase totals =	$1,117.81		$1,226.5347	$1,226.53	$1,226.55	$1,226.50