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	$186.99	6.502%	$199.1481	$199.15	$199.15	$199.10
Purchase #2	$211.25	9.802%	$231.9567	$231.96	$231.95	$232.00
Purchase #3	$87.82	3.138%	$90.5758	$90.58	$90.60	$90.60
Purchase #4	$79.77	3.864%	$82.8523	$82.85	$82.85	$82.90
Purchase #5	$90.73	13.685%	$103.1464	$103.15	$103.15	$103.10
Purchase #6	$222.90	3.472%	$230.6391	$230.64	$230.65	$230.60
Purchase #7	$177.72	3.357%	$183.6861	$183.69	$183.70	$183.70
7 purchase totals =	$1,057.18		$1,122.0045	$1,122.02	$1,122.05	$1,122.00