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	$176.47	3.609%	$182.8388	$182.84	$182.85	$182.80
Purchase #2	$121.54	8.218%	$131.5282	$131.53	$131.55	$131.50
Purchase #3	$116.44	11.720%	$130.0868	$130.09	$130.10	$130.10
Purchase #4	$200.29	11.815%	$223.9543	$223.95	$223.95	$224.00
Purchase #5	$141.98	3.782%	$147.3497	$147.35	$147.35	$147.30
Purchase #6	$115.74	6.641%	$123.4263	$123.43	$123.45	$123.40
Purchase #7	$137.35	3.543%	$142.2163	$142.22	$142.20	$142.20
7 purchase totals =	$1,009.81		$1,081.4004	$1,081.41	$1,081.45	$1,081.30