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	$124.53	9.506%	$136.3678	$136.37	$136.35	$136.40
Purchase #2	$68.54	4.683%	$71.7497	$71.75	$71.75	$71.70
Purchase #3	$201.86	8.372%	$218.7597	$218.76	$218.75	$218.80
Purchase #4	$97.59	10.147%	$107.4925	$107.49	$107.50	$107.50
Purchase #5	$59.39	10.161%	$65.4246	$65.42	$65.40	$65.40
Purchase #6	$199.84	5.870%	$211.5706	$211.57	$211.55	$211.60
Purchase #7	$229.61	8.834%	$249.8937	$249.89	$249.90	$249.90
7 purchase totals =	$981.36		$1,061.2586	$1,061.25	$1,061.20	$1,061.30