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	$231.96	12.306%	$260.505	$260.51	$260.50	$260.50
Purchase #2	$33.81	11.357%	$37.6498	$37.65	$37.65	$37.60
Purchase #3	$81.33	6.785%	$86.8482	$86.85	$86.85	$86.80
Purchase #4	$53.84	12.234%	$60.4268	$60.43	$60.45	$60.40
Purchase #5	$209.26	12.641%	$235.7126	$235.71	$235.70	$235.70
Purchase #6	$145.52	10.584%	$160.9218	$160.92	$160.90	$160.90
Purchase #7	$186.63	5.225%	$196.3814	$196.38	$196.40	$196.40
7 purchase totals =	$942.35		$1,038.4456	$1,038.45	$1,038.45	$1,038.30