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	$115.96	10.503%	$128.1393	$128.14	$128.15	$128.10
Purchase #2	$171.67	10.608%	$189.8808	$189.88	$189.90	$189.90
Purchase #3	$17.38	3.868%	$18.0523	$18.05	$18.05	$18.10
Purchase #4	$245.85	10.606%	$271.9249	$271.92	$271.90	$271.90
Purchase #5	$24.52	9.361%	$26.8153	$26.82	$26.80	$26.80
Purchase #6	$205.50	10.529%	$227.1371	$227.14	$227.15	$227.10
Purchase #7	$196.39	11.464%	$218.9041	$218.90	$218.90	$218.90
7 purchase totals =	$977.27		$1,080.8538	$1,080.85	$1,080.85	$1,080.80