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	$233.52	7.406%	$250.8145	$250.81	$250.80	$250.80
Purchase #2	$63.69	8.213%	$68.9209	$68.92	$68.90	$68.90
Purchase #3	$19.70	10.520%	$21.7724	$21.77	$21.75	$21.80
Purchase #4	$176.97	4.279%	$184.5425	$184.54	$184.55	$184.50
Purchase #5	$124.27	5.756%	$131.423	$131.42	$131.40	$131.40
Purchase #6	$168.53	4.721%	$176.4863	$176.49	$176.50	$176.50
Purchase #7	$31.79	5.722%	$33.609	$33.61	$33.60	$33.60
7 purchase totals =	$818.47		$867.5686	$867.56	$867.50	$867.50