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	$212.43	3.513%	$219.8927	$219.89	$219.90	$219.90
Purchase #2	$227.58	12.632%	$256.3279	$256.33	$256.35	$256.30
Purchase #3	$100.83	12.293%	$113.225	$113.23	$113.25	$113.20
Purchase #4	$189.85	11.529%	$211.7378	$211.74	$211.75	$211.70
Purchase #5	$64.97	8.585%	$70.5477	$70.55	$70.55	$70.50
Purchase #6	$177.57	7.183%	$190.3249	$190.32	$190.30	$190.30
Purchase #7	$94.68	11.371%	$105.4461	$105.45	$105.45	$105.40
7 purchase totals =	$1,067.91		$1,167.5021	$1,167.51	$1,167.55	$1,167.30