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	$168.80	11.275%	$187.8322	$187.83	$187.85	$187.80
Purchase #2	$79.37	4.451%	$82.9028	$82.90	$82.90	$82.90
Purchase #3	$133.45	5.326%	$140.5575	$140.56	$140.55	$140.60
Purchase #4	$240.85	6.638%	$256.8376	$256.84	$256.85	$256.80
Purchase #5	$232.61	12.545%	$261.7909	$261.79	$261.80	$261.80
Purchase #6	$178.94	4.344%	$186.7132	$186.71	$186.70	$186.70
Purchase #7	$240.39	9.815%	$263.9843	$263.98	$264.00	$264.00
7 purchase totals =	$1,274.41		$1,380.6185	$1,380.61	$1,380.65	$1,380.60