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	$99.36	8.550%	$107.8553	$107.86	$107.85	$107.90
Purchase #2	$183.51	9.716%	$201.3398	$201.34	$201.35	$201.30
Purchase #3	$53.69	11.298%	$59.7559	$59.76	$59.75	$59.80
Purchase #4	$212.79	11.140%	$236.4948	$236.49	$236.50	$236.50
Purchase #5	$233.45	3.717%	$242.1273	$242.13	$242.15	$242.10
Purchase #6	$148.30	13.291%	$168.0106	$168.01	$168.00	$168.00
Purchase #7	$134.59	4.308%	$140.3881	$140.39	$140.40	$140.40
7 purchase totals =	$1,065.69		$1,155.9718	$1,155.98	$1,156.00	$1,156.00