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	$203.70	6.300%	$216.5331	$216.53	$216.55	$216.50
Purchase #2	$39.60	7.658%	$42.6326	$42.63	$42.65	$42.60
Purchase #3	$57.67	7.525%	$62.0097	$62.01	$62.00	$62.00
Purchase #4	$41.58	12.353%	$46.7164	$46.72	$46.70	$46.70
Purchase #5	$5.91	6.308%	$6.2828	$6.28	$6.30	$6.30
Purchase #6	$228.53	10.816%	$253.2478	$253.25	$253.25	$253.20
Purchase #7	$76.95	6.730%	$82.1287	$82.13	$82.15	$82.10
7 purchase totals =	$653.94		$709.5511	$709.55	$709.60	$709.40