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	$52.36	9.467%	$57.3169	$57.32	$57.30	$57.30
Purchase #2	$233.28	13.863%	$265.6196	$265.62	$265.60	$265.60
Purchase #3	$232.93	4.515%	$243.4468	$243.45	$243.45	$243.40
Purchase #4	$112.59	3.467%	$116.4935	$116.49	$116.50	$116.50
Purchase #5	$171.29	7.146%	$183.5304	$183.53	$183.55	$183.50
Purchase #6	$206.94	7.521%	$222.504	$222.50	$222.50	$222.50
Purchase #7	$41.34	7.230%	$44.3289	$44.33	$44.35	$44.30
7 purchase totals =	$1,050.73		$1,133.2401	$1,133.24	$1,133.25	$1,133.10