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	$217.35	7.595%	$233.8577	$233.86	$233.85	$233.90
Purchase #2	$113.48	4.486%	$118.5707	$118.57	$118.55	$118.60
Purchase #3	$173.54	13.567%	$197.0842	$197.08	$197.10	$197.10
Purchase #4	$131.70	6.176%	$139.8338	$139.83	$139.85	$139.80
Purchase #5	$65.77	8.740%	$71.5183	$71.52	$71.50	$71.50
Purchase #6	$46.86	8.629%	$50.9035	$50.90	$50.90	$50.90
Purchase #7	$174.40	8.830%	$189.7995	$189.80	$189.80	$189.80
7 purchase totals =	$923.10		$1,001.5677	$1,001.56	$1,001.55	$1,001.60