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	$179.79	7.332%	$192.9722	$192.97	$192.95	$193.00
Purchase #2	$209.94	4.708%	$219.824	$219.82	$219.80	$219.80
Purchase #3	$91.75	11.766%	$102.5453	$102.55	$102.55	$102.50
Purchase #4	$243.66	4.158%	$253.7914	$253.79	$253.80	$253.80
Purchase #5	$131.65	12.313%	$147.8601	$147.86	$147.85	$147.90
Purchase #6	$125.80	10.843%	$139.4405	$139.44	$139.45	$139.40
Purchase #7	$76.54	11.653%	$85.4592	$85.46	$85.45	$85.50
7 purchase totals =	$1,059.13		$1,141.8927	$1,141.89	$1,141.85	$1,141.90