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	$57.85	8.196%	$62.5914	$62.59	$62.60	$62.60
Purchase #2	$142.80	5.310%	$150.3827	$150.38	$150.40	$150.40
Purchase #3	$11.54	4.333%	$12.04	$12.04	$12.05	$12.00
Purchase #4	$31.77	6.471%	$33.8258	$33.83	$33.85	$33.80
Purchase #5	$102.53	11.279%	$114.0944	$114.09	$114.10	$114.10
Purchase #6	$208.38	11.149%	$231.6123	$231.61	$231.60	$231.60
Purchase #7	$171.91	4.302%	$179.3056	$179.31	$179.30	$179.30
7 purchase totals =	$726.78		$783.8522	$783.85	$783.90	$783.80