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	$127.56	10.315%	$140.7178	$140.72	$140.70	$140.70
Purchase #2	$121.36	13.334%	$137.5421	$137.54	$137.55	$137.50
Purchase #3	$92.29	13.831%	$105.0546	$105.05	$105.05	$105.10
Purchase #4	$21.53	5.144%	$22.6375	$22.64	$22.65	$22.60
Purchase #5	$81.64	7.618%	$87.8593	$87.86	$87.85	$87.90
Purchase #6	$68.75	5.825%	$72.7547	$72.75	$72.75	$72.80
Purchase #7	$181.70	13.139%	$205.5736	$205.57	$205.55	$205.60
7 purchase totals =	$694.83		$772.1396	$772.13	$772.10	$772.20