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	$129.57	11.437%	$144.3889	$144.39	$144.40	$144.40
Purchase #2	$78.66	5.326%	$82.8494	$82.85	$82.85	$82.80
Purchase #3	$242.79	13.188%	$274.8091	$274.81	$274.80	$274.80
Purchase #4	$245.73	5.471%	$259.1739	$259.17	$259.15	$259.20
Purchase #5	$194.54	11.386%	$216.6903	$216.69	$216.70	$216.70
Purchase #6	$48.85	11.348%	$54.3935	$54.39	$54.40	$54.40
Purchase #7	$116.67	9.108%	$127.2963	$127.30	$127.30	$127.30
7 purchase totals =	$1,056.81		$1,159.6014	$1,159.60	$1,159.60	$1,159.60