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	$29.63	12.319%	$33.2801	$33.28	$33.30	$33.30
Purchase #2	$240.66	6.308%	$255.8408	$255.84	$255.85	$255.80
Purchase #3	$74.87	12.307%	$84.0843	$84.08	$84.10	$84.10
Purchase #4	$62.51	5.844%	$66.1631	$66.16	$66.15	$66.20
Purchase #5	$93.97	6.760%	$100.3224	$100.32	$100.30	$100.30
Purchase #6	$241.43	6.805%	$257.8593	$257.86	$257.85	$257.90
Purchase #7	$206.55	6.430%	$219.8312	$219.83	$219.85	$219.80
7 purchase totals =	$949.62		$1,017.3812	$1,017.37	$1,017.40	$1,017.40