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	$120.82	11.627%	$134.8677	$134.87	$134.85	$134.90
Purchase #2	$243.95	6.296%	$259.3091	$259.31	$259.30	$259.30
Purchase #3	$138.77	11.816%	$155.1671	$155.17	$155.15	$155.20
Purchase #4	$29.76	13.302%	$33.7187	$33.72	$33.70	$33.70
Purchase #5	$38.93	12.668%	$43.8617	$43.86	$43.85	$43.90
Purchase #6	$121.72	10.347%	$134.3144	$134.31	$134.30	$134.30
Purchase #7	$116.61	6.855%	$124.6036	$124.60	$124.60	$124.60
7 purchase totals =	$810.56		$885.8423	$885.84	$885.75	$885.90