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	$5.39	8.722%	$5.8601	$5.86	$5.85	$5.90
Purchase #2	$181.93	3.633%	$188.5395	$188.54	$188.55	$188.50
Purchase #3	$202.30	8.716%	$219.9325	$219.93	$219.95	$219.90
Purchase #4	$92.86	8.341%	$100.6055	$100.61	$100.60	$100.60
Purchase #5	$232.94	10.236%	$256.7837	$256.78	$256.80	$256.80
Purchase #6	$175.82	11.542%	$196.1131	$196.11	$196.10	$196.10
Purchase #7	$146.50	5.148%	$154.0418	$154.04	$154.05	$154.00
7 purchase totals =	$1,037.74		$1,121.8762	$1,121.87	$1,121.90	$1,121.80