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	$50.83	7.420%	$54.6016	$54.60	$54.60	$54.60
Purchase #2	$92.48	12.374%	$103.9235	$103.92	$103.90	$103.90
Purchase #3	$145.47	9.279%	$158.9682	$158.97	$158.95	$159.00
Purchase #4	$76.97	6.393%	$81.8907	$81.89	$81.90	$81.90
Purchase #5	$201.84	11.836%	$225.7298	$225.73	$225.75	$225.70
Purchase #6	$226.40	6.826%	$241.8541	$241.85	$241.85	$241.90
Purchase #7	$202.70	7.618%	$218.1417	$218.14	$218.15	$218.10
7 purchase totals =	$996.69		$1,085.1096	$1,085.10	$1,085.10	$1,085.10