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	$181.37	3.584%	$187.8703	$187.87	$187.85	$187.90
Purchase #2	$104.36	12.758%	$117.6742	$117.67	$117.65	$117.70
Purchase #3	$80.62	12.814%	$90.9506	$90.95	$90.95	$91.00
Purchase #4	$160.61	11.185%	$178.5742	$178.57	$178.55	$178.60
Purchase #5	$105.66	13.604%	$120.034	$120.03	$120.05	$120.00
Purchase #6	$232.65	11.684%	$259.8328	$259.83	$259.85	$259.80
Purchase #7	$143.27	9.275%	$156.5583	$156.56	$156.55	$156.60
7 purchase totals =	$1,008.54		$1,111.4944	$1,111.48	$1,111.45	$1,111.60