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	$209.99	7.517%	$225.7749	$225.77	$225.75	$225.80
Purchase #2	$40.47	8.542%	$43.9269	$43.93	$43.95	$43.90
Purchase #3	$102.82	6.453%	$109.455	$109.46	$109.45	$109.50
Purchase #4	$105.42	4.829%	$110.5107	$110.51	$110.50	$110.50
Purchase #5	$153.31	13.864%	$174.5649	$174.56	$174.55	$174.60
Purchase #6	$94.56	9.320%	$103.373	$103.37	$103.35	$103.40
Purchase #7	$149.60	12.114%	$167.7225	$167.72	$167.70	$167.70
7 purchase totals =	$856.17		$935.3279	$935.32	$935.25	$935.40