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	$201.34	6.360%	$214.1452	$214.15	$214.15	$214.10
Purchase #2	$191.85	3.127%	$197.8491	$197.85	$197.85	$197.80
Purchase #3	$32.75	6.510%	$34.882	$34.88	$34.90	$34.90
Purchase #4	$233.52	12.522%	$262.7614	$262.76	$262.75	$262.80
Purchase #5	$240.89	10.753%	$266.7929	$266.79	$266.80	$266.80
Purchase #6	$221.65	8.320%	$240.0913	$240.09	$240.10	$240.10
Purchase #7	$78.95	5.839%	$83.5599	$83.56	$83.55	$83.60
7 purchase totals =	$1,200.95		$1,300.0818	$1,300.08	$1,300.10	$1,300.10