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	$119.87	5.412%	$126.3574	$126.36	$126.35	$126.40
Purchase #2	$91.41	8.403%	$99.0912	$99.09	$99.10	$99.10
Purchase #3	$168.45	10.746%	$186.5516	$186.55	$186.55	$186.60
Purchase #4	$223.35	7.515%	$240.1348	$240.13	$240.15	$240.10
Purchase #5	$112.86	13.389%	$127.9708	$127.97	$127.95	$128.00
Purchase #6	$200.30	10.824%	$221.9805	$221.98	$222.00	$222.00
Purchase #7	$178.33	11.278%	$198.4421	$198.44	$198.45	$198.40
7 purchase totals =	$1,094.57		$1,200.5284	$1,200.52	$1,200.55	$1,200.60