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	$176.74	5.562%	$186.5703	$186.57	$186.55	$186.60
Purchase #2	$180.64	12.703%	$203.5867	$203.59	$203.60	$203.60
Purchase #3	$176.66	11.229%	$196.4972	$196.50	$196.50	$196.50
Purchase #4	$159.54	7.595%	$171.6571	$171.66	$171.65	$171.70
Purchase #5	$237.85	6.741%	$253.8835	$253.88	$253.90	$253.90
Purchase #6	$63.28	4.126%	$65.8909	$65.89	$65.90	$65.90
Purchase #7	$62.55	13.215%	$70.816	$70.82	$70.80	$70.80
7 purchase totals =	$1,057.26		$1,148.9017	$1,148.91	$1,148.90	$1,149.00