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	$217.94	6.385%	$231.8555	$231.86	$231.85	$231.90
Purchase #2	$118.85	8.637%	$129.1151	$129.12	$129.10	$129.10
Purchase #3	$128.87	10.626%	$142.5637	$142.56	$142.55	$142.60
Purchase #4	$228.83	6.833%	$244.466	$244.47	$244.45	$244.50
Purchase #5	$68.37	4.651%	$71.5499	$71.55	$71.55	$71.50
Purchase #6	$39.59	6.560%	$42.1871	$42.19	$42.20	$42.20
Purchase #7	$96.68	13.594%	$109.8227	$109.82	$109.80	$109.80
7 purchase totals =	$899.13		$971.5600	$971.57	$971.50	$971.60