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	$65.74	10.228%	$72.4639	$72.46	$72.45	$72.50
Purchase #2	$183.59	5.740%	$194.1281	$194.13	$194.15	$194.10
Purchase #3	$161.96	13.277%	$183.4634	$183.46	$183.45	$183.50
Purchase #4	$224.84	10.180%	$247.7287	$247.73	$247.75	$247.70
Purchase #5	$167.75	3.186%	$173.0945	$173.09	$173.10	$173.10
Purchase #6	$229.79	8.582%	$249.5106	$249.51	$249.50	$249.50
Purchase #7	$148.45	13.221%	$168.0766	$168.08	$168.10	$168.10
7 purchase totals =	$1,182.12		$1,288.4658	$1,288.46	$1,288.50	$1,288.50