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	$209.83	3.399%	$216.9621	$216.96	$216.95	$217.00
Purchase #2	$156.90	12.138%	$175.9445	$175.94	$175.95	$175.90
Purchase #3	$219.62	8.441%	$238.1581	$238.16	$238.15	$238.20
Purchase #4	$131.78	10.205%	$145.2281	$145.23	$145.25	$145.20
Purchase #5	$228.94	11.761%	$255.8656	$255.87	$255.85	$255.90
Purchase #6	$43.39	11.630%	$48.4363	$48.44	$48.45	$48.40
Purchase #7	$121.27	8.149%	$131.1523	$131.15	$131.15	$131.20
7 purchase totals =	$1,111.73		$1,211.7470	$1,211.75	$1,211.75	$1,211.80