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	$159.86	9.444%	$174.9572	$174.96	$174.95	$175.00
Purchase #2	$145.55	9.645%	$159.5883	$159.59	$159.60	$159.60
Purchase #3	$50.50	9.739%	$55.4182	$55.42	$55.40	$55.40
Purchase #4	$106.88	3.723%	$110.8591	$110.86	$110.85	$110.90
Purchase #5	$103.49	12.408%	$116.331	$116.33	$116.35	$116.30
Purchase #6	$151.72	3.426%	$156.9179	$156.92	$156.90	$156.90
Purchase #7	$59.43	5.614%	$62.7664	$62.77	$62.75	$62.80
7 purchase totals =	$777.43		$836.8381	$836.85	$836.80	$836.90