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	$73.71	6.849%	$78.7584	$78.76	$78.75	$78.80
Purchase #2	$10.50	6.341%	$11.1658	$11.17	$11.15	$11.20
Purchase #3	$234.91	10.512%	$259.6037	$259.60	$259.60	$259.60
Purchase #4	$69.97	12.293%	$78.5714	$78.57	$78.55	$78.60
Purchase #5	$139.42	3.455%	$144.237	$144.24	$144.25	$144.20
Purchase #6	$196.65	13.768%	$223.7248	$223.72	$223.70	$223.70
Purchase #7	$227.59	11.294%	$253.294	$253.29	$253.30	$253.30
7 purchase totals =	$952.75		$1,049.3551	$1,049.35	$1,049.30	$1,049.40