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	$199.38	8.334%	$215.9963	$216.00	$216.00	$216.00
Purchase #2	$111.82	5.672%	$118.1624	$118.16	$118.15	$118.20
Purchase #3	$216.53	5.484%	$228.4045	$228.40	$228.40	$228.40
Purchase #4	$155.46	6.228%	$165.142	$165.14	$165.15	$165.10
Purchase #5	$38.98	9.634%	$42.7353	$42.74	$42.75	$42.70
Purchase #6	$59.67	4.352%	$62.2668	$62.27	$62.25	$62.30
Purchase #7	$53.94	5.565%	$56.9418	$56.94	$56.95	$56.90
7 purchase totals =	$835.78		$889.6491	$889.65	$889.65	$889.60