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	$112.45	3.408%	$116.2823	$116.28	$116.30	$116.30
Purchase #2	$48.55	8.297%	$52.5782	$52.58	$52.60	$52.60
Purchase #3	$54.36	9.306%	$59.4187	$59.42	$59.40	$59.40
Purchase #4	$247.93	10.232%	$273.2982	$273.30	$273.30	$273.30
Purchase #5	$102.66	10.322%	$113.2566	$113.26	$113.25	$113.30
Purchase #6	$233.53	7.794%	$251.7313	$251.73	$251.75	$251.70
Purchase #7	$212.25	10.384%	$234.29	$234.29	$234.30	$234.30
7 purchase totals =	$1,011.73		$1,100.8553	$1,100.86	$1,100.90	$1,100.90