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	$161.78	6.568%	$172.4057	$172.41	$172.40	$172.40
Purchase #2	$104.61	6.867%	$111.7936	$111.79	$111.80	$111.80
Purchase #3	$121.63	10.292%	$134.1482	$134.15	$134.15	$134.10
Purchase #4	$206.93	8.513%	$224.546	$224.55	$224.55	$224.50
Purchase #5	$120.35	5.122%	$126.5143	$126.51	$126.50	$126.50
Purchase #6	$141.73	12.637%	$159.6404	$159.64	$159.65	$159.60
Purchase #7	$162.72	12.284%	$182.7085	$182.71	$182.70	$182.70
7 purchase totals =	$1,019.75		$1,111.7567	$1,111.76	$1,111.75	$1,111.60