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	$163.38	11.755%	$182.5853	$182.59	$182.60	$182.60
Purchase #2	$244.30	4.630%	$255.6111	$255.61	$255.60	$255.60
Purchase #3	$160.47	8.694%	$174.4213	$174.42	$174.40	$174.40
Purchase #4	$16.56	5.186%	$17.4188	$17.42	$17.40	$17.40
Purchase #5	$222.46	8.139%	$240.566	$240.57	$240.55	$240.60
Purchase #6	$135.40	6.755%	$144.5463	$144.55	$144.55	$144.50
Purchase #7	$33.60	4.285%	$35.0398	$35.04	$35.05	$35.00
7 purchase totals =	$976.17		$1,050.1886	$1,050.20	$1,050.15	$1,050.10