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	$219.31	13.576%	$249.0835	$249.08	$249.10	$249.10
Purchase #2	$197.76	9.526%	$216.5986	$216.60	$216.60	$216.60
Purchase #3	$204.56	4.607%	$213.9841	$213.98	$214.00	$214.00
Purchase #4	$165.37	12.121%	$185.4145	$185.41	$185.40	$185.40
Purchase #5	$95.57	10.835%	$105.925	$105.93	$105.95	$105.90
Purchase #6	$140.94	8.425%	$152.8142	$152.81	$152.80	$152.80
Purchase #7	$247.78	5.212%	$260.6943	$260.69	$260.70	$260.70
7 purchase totals =	$1,271.29		$1,384.5142	$1,384.50	$1,384.55	$1,384.50