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	$179.98	3.296%	$185.9121	$185.91	$185.90	$185.90
Purchase #2	$99.60	10.681%	$110.2383	$110.24	$110.25	$110.20
Purchase #3	$6.75	13.488%	$7.6604	$7.66	$7.65	$7.70
Purchase #4	$170.48	13.132%	$192.8674	$192.87	$192.85	$192.90
Purchase #5	$147.54	8.782%	$160.497	$160.50	$160.50	$160.50
Purchase #6	$52.57	13.845%	$59.8483	$59.85	$59.85	$59.80
Purchase #7	$130.89	10.342%	$144.4266	$144.43	$144.45	$144.40
7 purchase totals =	$787.81		$861.4501	$861.46	$861.45	$861.40