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	$177.59	4.187%	$185.0257	$185.03	$185.05	$185.00
Purchase #2	$164.84	12.218%	$184.9802	$184.98	$185.00	$185.00
Purchase #3	$53.84	3.458%	$55.7018	$55.70	$55.70	$55.70
Purchase #4	$90.34	6.284%	$96.017	$96.02	$96.00	$96.00
Purchase #5	$196.55	8.282%	$212.8283	$212.83	$212.85	$212.80
Purchase #6	$213.98	6.303%	$227.4672	$227.47	$227.45	$227.50
Purchase #7	$123.71	6.584%	$131.8551	$131.86	$131.85	$131.90
7 purchase totals =	$1,020.85		$1,093.8753	$1,093.89	$1,093.90	$1,093.90