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	$67.54	13.310%	$76.5296	$76.53	$76.55	$76.50
Purchase #2	$111.85	13.176%	$126.5874	$126.59	$126.60	$126.60
Purchase #3	$129.58	13.192%	$146.6742	$146.67	$146.65	$146.70
Purchase #4	$62.45	10.666%	$69.1109	$69.11	$69.10	$69.10
Purchase #5	$165.63	4.264%	$172.6925	$172.69	$172.70	$172.70
Purchase #6	$187.77	6.322%	$199.6408	$199.64	$199.65	$199.60
Purchase #7	$85.59	12.281%	$96.1013	$96.10	$96.10	$96.10
7 purchase totals =	$810.41		$887.3367	$887.33	$887.35	$887.30