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	$213.58	7.389%	$229.3614	$229.36	$229.35	$229.40
Purchase #2	$111.58	7.156%	$119.5647	$119.56	$119.55	$119.60
Purchase #3	$119.47	7.421%	$128.3359	$128.34	$128.35	$128.30
Purchase #4	$201.86	4.236%	$210.4108	$210.41	$210.40	$210.40
Purchase #5	$57.33	5.228%	$60.3272	$60.33	$60.35	$60.30
Purchase #6	$128.89	12.332%	$144.7847	$144.78	$144.80	$144.80
Purchase #7	$94.45	11.647%	$105.4506	$105.45	$105.45	$105.50
7 purchase totals =	$927.16		$998.2353	$998.23	$998.25	$998.30