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	$122.40	4.818%	$128.2972	$128.30	$128.30	$128.30
Purchase #2	$174.46	6.263%	$185.3864	$185.39	$185.40	$185.40
Purchase #3	$15.85	11.108%	$17.6106	$17.61	$17.60	$17.60
Purchase #4	$178.81	13.478%	$202.91	$202.91	$202.90	$202.90
Purchase #5	$99.38	10.178%	$109.4949	$109.49	$109.50	$109.50
Purchase #6	$230.71	6.309%	$245.2655	$245.27	$245.25	$245.30
Purchase #7	$72.59	7.500%	$78.0343	$78.03	$78.05	$78.00
7 purchase totals =	$894.20		$966.9989	$967.00	$967.00	$967.00