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	$55.98	9.822%	$61.4784	$61.48	$61.50	$61.50
Purchase #2	$204.86	13.539%	$232.596	$232.60	$232.60	$232.60
Purchase #3	$24.69	3.132%	$25.4633	$25.46	$25.45	$25.50
Purchase #4	$77.63	9.841%	$85.2696	$85.27	$85.25	$85.30
Purchase #5	$200.83	8.201%	$217.3001	$217.30	$217.30	$217.30
Purchase #6	$171.54	3.669%	$177.8338	$177.83	$177.85	$177.80
Purchase #7	$198.75	12.152%	$222.9021	$222.90	$222.90	$222.90
7 purchase totals =	$934.28		$1,022.8433	$1,022.84	$1,022.85	$1,022.90