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	$181.56	3.666%	$188.216	$188.22	$188.20	$188.20
Purchase #2	$247.37	3.428%	$255.8498	$255.85	$255.85	$255.80
Purchase #3	$198.89	10.499%	$219.7715	$219.77	$219.75	$219.80
Purchase #4	$36.34	8.576%	$39.4565	$39.46	$39.45	$39.50
Purchase #5	$137.78	13.473%	$156.3431	$156.34	$156.35	$156.30
Purchase #6	$213.53	9.369%	$233.5356	$233.54	$233.55	$233.50
Purchase #7	$247.30	8.309%	$267.8482	$267.85	$267.85	$267.80
7 purchase totals =	$1,262.77		$1,361.0207	$1,361.03	$1,361.00	$1,360.90