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	6.503%	$233.5717	$233.57	$233.55	$233.60
Purchase #2	$81.64	10.398%	$90.1289	$90.13	$90.15	$90.10
Purchase #3	$17.98	5.647%	$18.9953	$19.00	$19.00	$19.00
Purchase #4	$144.47	5.505%	$152.4231	$152.42	$152.40	$152.40
Purchase #5	$170.76	13.795%	$194.3163	$194.32	$194.30	$194.30
Purchase #6	$162.99	3.296%	$168.3622	$168.36	$168.35	$168.40
Purchase #7	$121.34	6.182%	$128.8412	$128.84	$128.85	$128.80
7 purchase totals =	$918.49		$986.6387	$986.64	$986.60	$986.60