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	$202.75	11.443%	$225.9507	$225.95	$225.95	$226.00
Purchase #2	$139.56	13.639%	$158.5946	$158.59	$158.60	$158.60
Purchase #3	$163.68	7.127%	$175.3455	$175.35	$175.35	$175.30
Purchase #4	$46.28	12.441%	$52.0377	$52.04	$52.05	$52.00
Purchase #5	$165.29	12.716%	$186.3083	$186.31	$186.30	$186.30
Purchase #6	$31.47	6.807%	$33.6122	$33.61	$33.60	$33.60
Purchase #7	$223.74	13.154%	$253.1708	$253.17	$253.15	$253.20
7 purchase totals =	$972.77		$1,085.0198	$1,085.02	$1,085.00	$1,085.00