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	$41.95	13.817%	$47.7462	$47.75	$47.75	$47.70
Purchase #2	$225.95	7.249%	$242.3291	$242.33	$242.35	$242.30
Purchase #3	$102.46	4.406%	$106.9744	$106.97	$106.95	$107.00
Purchase #4	$98.71	4.703%	$103.3523	$103.35	$103.35	$103.40
Purchase #5	$118.71	10.838%	$131.5758	$131.58	$131.60	$131.60
Purchase #6	$214.53	4.351%	$223.8642	$223.86	$223.85	$223.90
Purchase #7	$219.48	11.526%	$244.7773	$244.78	$244.80	$244.80
7 purchase totals =	$1,021.79		$1,100.6193	$1,100.62	$1,100.65	$1,100.70