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	$162.46	3.417%	$168.0113	$168.01	$168.00	$168.00
Purchase #2	$154.71	7.310%	$166.0193	$166.02	$166.00	$166.00
Purchase #3	$48.96	10.865%	$54.2795	$54.28	$54.30	$54.30
Purchase #4	$231.34	4.287%	$241.2575	$241.26	$241.25	$241.30
Purchase #5	$143.41	8.300%	$155.313	$155.31	$155.30	$155.30
Purchase #6	$148.74	3.702%	$154.2464	$154.25	$154.25	$154.20
Purchase #7	$150.33	9.428%	$164.5031	$164.50	$164.50	$164.50
7 purchase totals =	$1,039.95		$1,103.6301	$1,103.63	$1,103.60	$1,103.60